ScholarBank@NUShttps://scholarbank.nus.edu.sgThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Fri, 20 Sep 2019 03:53:08 GMT2019-09-20T03:53:08Z502161- Comment on "Anomalous Heat Conduction and Anomalous Diffusion in One-Dimensional Systems" [1] (multiple letters)https://scholarbank.nus.edu.sg/handle/10635/111658Title: Comment on "Anomalous Heat Conduction and Anomalous Diffusion in One-Dimensional Systems" [1] (multiple letters)
Authors: Metzler, R.; Sokolov, I.M.; Li, B.; Wang, J.
Fri, 27 Feb 2004 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1116582004-02-27T00:00:00Z
- Stability of quantum motion: A semiclassical approachhttps://scholarbank.nus.edu.sg/handle/10635/98895Title: Stability of quantum motion: A semiclassical approach
Authors: Wang, W.-G.; Li, B.
Abstract: A semiclassical theory is used for the study of fidelity. For systems with weak chaos in the classical limit, we show that the fidelity has a non-Fermi-Golden-Rule decay, which can be explained by the closeness of the distribution of action difference in the semiclassical theory to the Levy distribution. For systems with strong chaos in the classical limit, we present a semiclassical expression for fidelity decay in the Lyapunov regime, which is more general than the previously predicted Lyapunov decay and λ1 decay of fidelity. For systems with regular motion in the classical limit, we derive the fidelity decay for initial narrow Gaussian wavepackets, which displays a quite complex behaviour, from Gaussian to power law decay t-α with 1 ≤ α ≤ 2. © World Scientific Publishing Company.
Sun, 30 Sep 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/988952007-09-30T00:00:00Z
- Heat conduction in one-dimensional nonintegrable systemshttps://scholarbank.nus.edu.sg/handle/10635/96768Title: Heat conduction in one-dimensional nonintegrable systems
Authors: Hu, B.; Li, B.; Zhao, H.
Abstract: Two classes of one-dimensional nonintegrahle systems represented by the Fermi-Pasta-Ulam (FPU) model and the discrete φ4 model are studied to seek a generic mechanism of energy transport on a microscopic level sustaining macroscopic behaviors. The results enable us to understand why the class represented by the φ4 model has a normal thermal conductivity and the class represented by the FPU model does not even though the temperature gradient can be established.
Sat, 01 Apr 2000 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/967682000-04-01T00:00:00Z
- Anomalous Thermal Transport in Nanostructureshttps://scholarbank.nus.edu.sg/handle/10635/98966Title: Anomalous Thermal Transport in Nanostructures
Authors: Zhang, G.; Liu, S.; Li, B.
Abstract: Thermal transport in nanoscale structures has attracted an increasing attention in the past two decades. Here we give a brief overview of the recent developments in experimental and theoretical studies of heat transport in nanomaterials such as nanotubes and nanowires. In particular, we will demonstrate that the phonons in nanotubes and nanowires transport superdiffusively, which leads to a length-dependent thermal conductivity. In other words, heat conduction in low-dimensional nanostructures does not obey Fourier's law. © 2013 Wiley-VCH Verlag GmbH & Co. KGaA.
Mon, 11 Feb 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/989662013-02-11T00:00:00Z
- Anomalous heat conduction and anomalous diffusion in one-dimensional systemshttps://scholarbank.nus.edu.sg/handle/10635/116230Title: Anomalous heat conduction and anomalous diffusion in one-dimensional systems
Authors: Li, B.; Wang, J.
Abstract: A connection between anomalous heat conduction and anomalous diffusion in 1D systems was established. The central result includes all possible cases observed in different classes of 1D models, ranging from sub diffusion, normal diffusion, and superdiffusion to ballistic transport.
Fri, 25 Jul 2003 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1162302003-07-25T00:00:00Z
- Electronic transport in hybrid mesoscopic structures: A nonequilibrium Green function approachhttps://scholarbank.nus.edu.sg/handle/10635/96437Title: Electronic transport in hybrid mesoscopic structures: A nonequilibrium Green function approach
Authors: Zeng, Z.Y.; Li, B.; Claro, F.
Abstract: We present a unified transport theory of hybrid structures, in which a confined normal state (N) sample is sandwiched between two leads each of which can be either a ferromagnet (F) or a superconductor (S) via tunnel barriers. By introducing a four-dimensional Nambu-spinor space, a general current formula is derived within the Keldysh nonequilibrium Green function formalism, which can be applied to various kinds of hybrid mesoscopic systems with strong correlations even in the nonequilibrium situation. Such a formula is gauge invariant. We also demonstrate analytically for some quantities, such as the difference between chemical potentials, superconductor order parameter phases, and ferromagnetic magnetization orientations, that only their relative value appears explicitly in the current expression. When applied to specific structures, the formula becomes of the Meir-Wingreen-type favoring strong correlation effects, and reduces to the Landauer-Büttiker-type in noninteracting systems such as the double-barrier resonant structures, which we study in detail beyond the wide-band approximation. We find that the spin-dependent density of states of the ferromagnetic lead(s) is reflected in the resonant peak and resonant shoulder structure of the 1-V characteristics of F/I/N/I/F structures with large level spacing. The tunnel magnetoresistance that exhibits complex behaviors as a function of the bias voltage, can be either positive or negative, suppressed or enhanced within the resonant peak region(s), depending on the couplings to the leads. The Andreev current spectrum of F/I/N/I/S structures consists of a series of resonant peaks as a function of the gate voltage, of which the number and amplitude are strongly dependent on the bias voltage, degree of spin polarization of the ferromagnetic lead, energy gap of the superconducting lead, and the level configuration of the central region. In S/I/N/I/S resonant structures with asymmetric superconducting energy gaps, the Josephson current through a single resonant level is slightly enhanced in contrast to the significant enhancement of the Josephson current in S/N/S junctions. The current-phase relation is relevant to the level position and the couplings to the superconducting leads.
Mon, 01 Sep 2003 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/964372003-09-01T00:00:00Z
- Heat conductivity in linear mixing systemshttps://scholarbank.nus.edu.sg/handle/10635/116383Title: Heat conductivity in linear mixing systems
Authors: Li, B.; Casati, G.; Wang, J.
Abstract: A study of heat conductivity in linear mixing system was carried out. A quasi-one-dimensional channel with triangular scatterers with internal angles was also investigated. The numerical value of the thermal conductivity computed via a Green-Kubo approach agrees with that obtained by direct numerical simulations with thermal baths.
Sat, 01 Feb 2003 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1163832003-02-01T00:00:00Z
- Electronic properties of the 1D Frenkel-Kontorova modelhttps://scholarbank.nus.edu.sg/handle/10635/96427Title: Electronic properties of the 1D Frenkel-Kontorova model
Authors: Tong, P.; Li, B.; Hu, B.
Abstract: Electronic properties of one-dimensional Frenkel-Kontorova (FK) model was were studied. The energy spectra and quantum diffusion of an electron was studied numerically in FK chains. Electron eigenenergies were obtained numerically by the transfer matrix method. Different behaviors were observed for the spectral and dynamical properties of an electron display in the invariance circle regime and in the Cantorus regime. The relationship between transport and spectral properties was also discussed.
Mon, 28 Jan 2002 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/964272002-01-28T00:00:00Z
- Interface thermal resistance between Frenkel-Kontorova and Fermi-Pasta-Ulam latticeshttps://scholarbank.nus.edu.sg/handle/10635/98762Title: Interface thermal resistance between Frenkel-Kontorova and Fermi-Pasta-Ulam lattices
Authors: Lan, J.; Wang, L.; Li, B.
Abstract: By connecting two dissimilar anharmonic lattices exemplified by Fermi-Pasta-Ulam (FPU) model and Frenkel-kontorova (FK) model, we successfully build up one dimensional thermal diode. We find the rectifying effect is closely related to asymmetric interface thermal resistance ( Kapitza resistance). And the asymmetric thermal resistance depends on how the temperature gradient is applied. Moreover, a quatitative relationship between the thermal rectification and the phonon spectra is propsoed. © World Scientific Publishing Company.
Sun, 30 Sep 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/987622007-09-30T00:00:00Z
- International Journal of Modern Physics: Prefacehttps://scholarbank.nus.edu.sg/handle/10635/98763Title: International Journal of Modern Physics: Preface
Authors: Li, B.; Tang, L.-H.
Sun, 30 Sep 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/987632007-09-30T00:00:00Z
- Size-dependent melting temperature and thermal conductivity of nanoscale semiconductorshttps://scholarbank.nus.edu.sg/handle/10635/98882Title: Size-dependent melting temperature and thermal conductivity of nanoscale semiconductors
Authors: Liang, L.H.; Li, B.
Abstract: A model describing size-dependent melting temperature and thermal conductivity of nanosemiconductors is proposed based on Lindermann's melting criterion and Debye model. By the atomic thermal vibration consideration and by introducing intrinsic size effect of phonon velocity and mean free path combined with surface scattering effect, the model predicts that the melting temperature and thermal conductivity of nanosemiconductors decrease as the size reduces. The size effect depends on such material parameters as the vibration entropy, mean free path, the characteristic crystal size and surface roughness. The predictions are in agreement with experimental results of Si nanoparticles, nanowires and thin films. © World Scientific Publishing Company.
Sun, 30 Sep 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/988822007-09-30T00:00:00Z
- Pumping current in a quantum dot by an oscillating magnetic fieldhttps://scholarbank.nus.edu.sg/handle/10635/98859Title: Pumping current in a quantum dot by an oscillating magnetic field
Authors: Zhao, Y.Z.; Li, H.; Li, B.
Abstract: We investigate spin and charge current through a quantum dot pumped by a time-varying magnetic field. Using the density matrix method, quantum rate equations for the electronic occupation numbers in the quantum dot are obtained and solved in the stationary state limit for a wide set of parameters. Both charge and spin currents are expressed explicitly in terms of several relevant parameters and analyzed in detail. The results suggest a way of optimizing experimental parameters to obtain an maximal spin current without the charge current flow. © World Scientific Publishing Company.
Sun, 30 Sep 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/988592007-09-30T00:00:00Z
- Bipolaron dynamics in non-degenerate polymershttps://scholarbank.nus.edu.sg/handle/10635/98644Title: Bipolaron dynamics in non-degenerate polymers
Authors: Yan, Y.-H.; Wu, C.-Q.; Li, B.-W.
Abstract: Bipolaron dynamics in non-degenerate polymers are discussed using the nonadiabatic dynamic method. First, charge injection process from metal electrode to a nondegenerate polymer in a metal/polymer/metal structure has been investigated. We demonstrate that the dynamical formation of a bipolaron sensitively depends on the work function of metal electrode. We also study the bipolaron dissociation process. It is found that the electric field that can dissociate the bipoalron is up to 106 V/cm, which is consistent with experiments. © World Scientific Publishing Company.
Sun, 30 Sep 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/986442007-09-30T00:00:00Z
- Disturbance spreading in incommensurate and quasiperiodic systemshttps://scholarbank.nus.edu.sg/handle/10635/96257Title: Disturbance spreading in incommensurate and quasiperiodic systems
Authors: Hu, B.; Li, B.; Tong, P.
Abstract: The propagation of an initially localized excitation in one-dimensional incommensurate, quasiperiodic and random systems is investigated numerically. It is discovered that the time evolution of variances σ2(t) of atom displacements depends on the initial condition. For the initial condition with nonzero momentum, σ2(t) goes as tα with α=1 and 0 for incommensurate Frenkel-Kontorova model at V below and above Vc respectively, and α=1 for uniform, quasiperiodic and random chains. It is also found that α=1-β with β the exponent of distribution function of frequency at zero frequency, i.e., ρ(ω)∼ωβ (as ω→0). For the initial condition with zero momentum, α=0 for all systems studied. The underlying physical meaning of this diffusive behavior is discussed. ©2000 The American Physical Society.
Sat, 01 Apr 2000 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/962572000-04-01T00:00:00Z
- Intriguing Heat Conduction of a Chain with Transverse Motionshttps://scholarbank.nus.edu.sg/handle/10635/96973Title: Intriguing Heat Conduction of a Chain with Transverse Motions
Authors: Wang, J.-S.; Li, B.
Abstract: Heat conduction in a one-dimensional chain of particles was investigated. The particles were connected by two-dimensional harmonic springs. A simple mode-coupling analysis was performed. Three types of thermal conducting behaviors were found using equilibrium and nonequlibrium molecular dynamics. It was suggested that power-law divergence should be a generic feature for such models.
Fri, 20 Feb 2004 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/969732004-02-20T00:00:00Z
- Heat switch and modulator: A model of thermal transistorhttps://scholarbank.nus.edu.sg/handle/10635/98735Title: Heat switch and modulator: A model of thermal transistor
Authors: Wang, L.; Li, B.
Abstract: A model of a thermal transistor to control heat flow is reported. Like its electronic counterpart, the thermal transistor is a three-terminal device with the important feature that the heat current through two terminals can be switched or modulated by the temperature of the third terminal. The thermal transistor model is possible because of the negative differential thermal resistance. © World Scientific Publishing Company.
Sun, 30 Sep 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/987352007-09-30T00:00:00Z
- Finite thermal conductivity in 1D models having zero Lyapunov exponentshttps://scholarbank.nus.edu.sg/handle/10635/96637Title: Finite thermal conductivity in 1D models having zero Lyapunov exponents
Authors: Li, B.; Wang, L.; Hu, B.
Abstract: Heat conduction was studied in different 1D Ehrenfest channels. It was found that the temperature gradient can be formed in all cases. However, a finite thermal conductivity was reached only when the disorder exists. It was concluded that the finite thermal conductivity might have nothing to do with the underlying dynamics.
Mon, 03 Jun 2002 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/966372002-06-03T00:00:00Z
- Metabolic network analysis revealed distinct routes of deletion effects between essential and non-essential geneshttps://scholarbank.nus.edu.sg/handle/10635/97177Title: Metabolic network analysis revealed distinct routes of deletion effects between essential and non-essential genes
Authors: Ma, J.; Zhang, X.; Ung, C.Y.; Chen, Y.Z.; Li, B.
Abstract: Interest in essential genes has arisen recently given their importance in antimicrobial drug development. Although knockouts of essential genes are commonly known to cause lethal phenotypes, there is insufficient understanding on the intermediate changes followed by genetic perturbation and to what extent essential genes correlate to other genes. Here, we characterized the gene knockout effects by using a list of affected genes, termed as 'damage lists'. These damage lists were identified through a refined cascading failure approach that was based on a previous topological flux balance analysis. Using an Escherichia coli metabolic network, we incorporated essentiality information into damage lists and revealed that the knockout of an essential gene mainly affects a large range of other essential genes whereas knockout of a non-essential gene only interrupts other non-essential genes. Also, genes sharing common damage lists tend to have the same essentiality. We extracted 72 core functional modules from the common damage lists of essential genes and demonstrated their ability to halt essential metabolites production. Overall, our network analysis revealed that essential and non-essential genes propagated their deletion effects via distinct routes, conferring mechanistic explanation to the observed lethality phenotypes of essential genes. © 2012 The Royal Society of Chemistry.
Thu, 01 Mar 2012 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/971772012-03-01T00:00:00Z
- Topological magnon insulator in insulating ferromagnethttps://scholarbank.nus.edu.sg/handle/10635/98420Title: Topological magnon insulator in insulating ferromagnet
Authors: Zhang, L.; Ren, J.; Wang, J.-S.; Li, B.
Abstract: In the ferromagnetic insulator with the Dzyaloshinskii-Moriya interaction, we theoretically predict and numerically verify a topological magnon insulator, where the charge-free magnon is topologically protected for transporting along the edge/surface while it is insulating in the bulk. The chiral edge states form a connected loop as a 4π- or 8π-period Möbius strip in the spin-wave vector space, showing the nontrivial topology of magnonic bands. Using the nonequilibrium Green's function method, we explicitly demonstrate that the one-way chiral edge transport is indeed topologically protected from defects or disorders. Moreover, we show that the topological edge state mainly localizes around edges and leaks into the bulk with oscillatory decay. Although the chiral edge magnons and energy current prefer to travel along one edge from the hot region to the cold one, the anomalous transports are identified in the opposite edge, which reversely flow from the cold region to the hot one. Our findings could be validated within wide energy ranges in various magnonic crystals, such as Lu2V2O7. © 2013 American Physical Society.
Mon, 08 Apr 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/984202013-04-08T00:00:00Z
- Thermal conductivity of composites with nanoscale inclusions and size-dependent percolationhttps://scholarbank.nus.edu.sg/handle/10635/98348Title: Thermal conductivity of composites with nanoscale inclusions and size-dependent percolation
Authors: Liang, L.H.; Wei, Y.G.; Li, B.
Abstract: An analytical model for thermal conductivity of composites with nanoparticles in a matrix is developed based on the effective medium theory by introducing the intrinsic size effect of thermal conductivity of nanoparticles and the interface thermal resistance effect between two phases. The model predicts the percolation of thermal conductivity with the volume fraction change of the second phase, and the percolation threshold depends on the size and the shape of the nanoparticles. The theoretical predictions are in agreement with the experimental results. © 2008 IOP Publishing Ltd.
Wed, 10 Sep 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/983482008-09-10T00:00:00Z
- Ultralow thermal conductivity of isotope-doped silicon nanowireshttps://scholarbank.nus.edu.sg/handle/10635/98504Title: Ultralow thermal conductivity of isotope-doped silicon nanowires
Authors: Yang, N.; Zhang, G.; Li, B.
Abstract: The thermal conductivity of silicon nanowires (SiNWs) is investigated by molecular dynamics (MD) simulation. It is found that the thermal conductivity of SiNWs can be reduced exponentially by isotopic defects at room temperature. The thermal conductivity reaches the minimum, which is about 27% of that of pure 28Si NW, when doped with 50% isotope atoms. The thermal conductivity of isotopic-superlattice structured SiNWs depends clearly on the period of superlattice. At a critical period of 1.09 nm, the thermal conductivity is only 25% of the value of pure Si NW. An anomalous enhancement of thermal conductivity is observed when the superlattice period is smaller than this critical length. The ultralow thermal conductivity of superlattice structured SiNWs is explained with phonon spectrum theory. © 2008 American Chemical Society.
Tue, 01 Jan 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/985042008-01-01T00:00:00Z
- Unraveled mechanism in silk engineering: Fast reeling induced silk tougheninghttps://scholarbank.nus.edu.sg/handle/10635/98533Title: Unraveled mechanism in silk engineering: Fast reeling induced silk toughening
Authors: Wu, X.; Liu, X.-Y.; Du, N.; Xu, G.; Li, B.
Abstract: We theoretically and experimentally study the mechanical response of silkworm and spider silks against stretching and the relationship with the underlying structural factors. It is found that the typical stress-strain profiles are predicted in good agreement with experimental measurements by implementing the " Β -sheet splitting" mechanism we discovered and verified, primarily varying the secondary structure of protein macromolecules. The functions of experimentally observed structural factors responding to the external stress have been clearly addressed, and optimization of the microscopic structures to enhance the mechanical strength will be pointed out, beneficial to their biomedical and textile applications. © 2009 American Institute of Physics.
Thu, 01 Jan 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/985332009-01-01T00:00:00Z
- Wall "thickness" effects on Raman spectrum shift, thermal conductivity, and Young's modulus of single-walled nanotubeshttps://scholarbank.nus.edu.sg/handle/10635/98571Title: Wall "thickness" effects on Raman spectrum shift, thermal conductivity, and Young's modulus of single-walled nanotubes
Authors: Zhang, G.; Li, B.
Abstract: We demonstrate that at a finite temperature, an effective wall thickness of a single-walled carbon nanotube (SWNT) should be W = W s + W d where W s is the static thickness defined as the extension of the outmost electronic orbit and W d the dynamic thickness due to thermal vibration of atoms. Both molecular simulations and a theoretical analysis show that W d is proportional to T 1/2. We find that the increase of dynamic thickness with temperature is the main mechanism of Raman spectrum shift. The introduction of the dynamic thickness changes some conclusions about Young's modulus and reduces the values of thermal conductivity. © 2005 American Chemical Society.
Thu, 22 Dec 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/985712005-12-22T00:00:00Z
- Wave-packet rectification in nonlinear electronic systems: A tunable Aharonov-Bohm diodehttps://scholarbank.nus.edu.sg/handle/10635/98575Title: Wave-packet rectification in nonlinear electronic systems: A tunable Aharonov-Bohm diode
Authors: Li, Y.; Zhou, J.; Marchesoni, F.; Li, B.
Abstract: Rectification of electron wave-packets propagating along a quasi-one dimensional chain is commonly achieved via the simultaneous action of nonlinearity and longitudinal asymmetry, both confined to a limited portion of the chain termed wave diode. However, it is conceivable that, in the presence of an external magnetic field, spatial asymmetry perpendicular to the direction of propagation suffices to ensure rectification. This is the case of a nonlinear ring-shaped lattice with different upper and lower halves (diode), which is attached to two elastic chains (leads). The resulting device is mirror symmetric with respect to the ring vertical axis, but mirror asymmetric with respect to the chain direction. Wave propagation along the two diode paths can be modeled for simplicity by a discrete Schrödinger equation with cubic nonlinearities. Numerical simulations demonstrate that, thanks to the Aharonov-Bohm effect, such a diode can be operated by tuning the magnetic flux across the ring.
Wed, 02 Apr 2014 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/985752014-04-02T00:00:00Z
- Universal statistics of wave functions in chaotic and disordered systemshttps://scholarbank.nus.edu.sg/handle/10635/98531Title: Universal statistics of wave functions in chaotic and disordered systems
Authors: Hu, B.; Li, B.; Wang, W.
Abstract: We study a new statistics of wave functions in several chaotic and disordered systems: the random matrix model, band random matrix model, the Lipkin model, chaotic quantum billiard and the ID tight-binding model. Both numerical and analytical results show that the distribution function of a generalized Riccati variable, defined as the ratio of components of eigenfunctions on basis states coupled by perturbation, is universal, and has the form of a Lorentzian distribution.
Mon, 01 May 2000 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/985312000-05-01T00:00:00Z
- General initial value form of the semiclassical propagatorhttps://scholarbank.nus.edu.sg/handle/10635/114334Title: General initial value form of the semiclassical propagator
Authors: Hu, B.; Jie, Q.; Li, B.; Wang, S.
Abstract: An idea similar to the block approach used to calculate the path integral of a quantum propagator was employed to obtain a general initial value form of the semiclassical propagator. The semiclassical propagator formulation involves only nearby orbit approximation. The simple initial value form of the semiclassical propagator is nonsingular everywhere is efficient for numeric implementation. A generalized formulation is obtained with the block idea. The initial value form maintains the accuracy with a properly specified weight function.
Sun, 01 Apr 2001 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1143342001-04-01T00:00:00Z
- Phononics: A new science and technology of controlling heat flow and processing information by phononshttps://scholarbank.nus.edu.sg/handle/10635/53310Title: Phononics: A new science and technology of controlling heat flow and processing information by phonons
Authors: Wang, L.; Zhang, G.; Wu, G.; Yang, N.; Li, B.
Abstract: Heat due to lattice vibration (phonons) is traditionally regarded as harmful for information processing. In this paper, we will demonstrate via numerical simulation, theoretical analysis and experiments that, phonons, can be manipulated like electrons. They can be used to carry and process information. Basic phononic devices such as thermal diode, thermal transistor, thermal logic gate and thermal memory will be discussed via nonlinear lattice model. Moreover, we will also discuss how to manipulate and tune thermal conductivity of nanostructure so that to control heat flow. Both theoretical and experimental works will be shown. © 2010 by ASME.
Fri, 01 Jan 2010 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/533102010-01-01T00:00:00Z
- Anomalous heat conduction, diffusion and heat rectification in nanoscale structureshttps://scholarbank.nus.edu.sg/handle/10635/53274Title: Anomalous heat conduction, diffusion and heat rectification in nanoscale structures
Authors: Zhang, G.; Yang, N.; Wu, G.; Li, B.
Abstract: In this paper, we report the recent developments in the study of heat transport in nano materials. First of all, we show that phonon transports in nanotube super-diffusively which leads to a length dependence thermal conductivity, thus breaks down the Fourier law. Then we discuss how the introduction of isotope doping can reduce the thermal conductivity efficiently. The theoretical results are in good agreement with experimental ones. Finally, we will demonstrate that nanoscale structures are promising candidates for heat rectification. Copyright © 2009 by ASME.
Fri, 01 Jan 2010 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/532742010-01-01T00:00:00Z
- Phononics gets hothttps://scholarbank.nus.edu.sg/handle/10635/97530Title: Phononics gets hot
Authors: Wang, L.; Li, B.
Sat, 01 Mar 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/975302008-03-01T00:00:00Z
- Geometric heat flux for classical thermal transport in interacting open systemshttps://scholarbank.nus.edu.sg/handle/10635/96715Title: Geometric heat flux for classical thermal transport in interacting open systems
Authors: Ren, J.; Liu, S.; Li, B.
Abstract: We study classical heat conduction in a dissipative open system composed of interacting oscillators. By exactly solving a twisted Fokker-Planck equation which describes the full counting statistics of heat flux flowing through the system, we identify the geometric-phase-like effect and examine its impact on the classical heat transport. We find that the nonlinear interaction as well as the closely related temperature dependence of system parameters are crucial in manifesting the geometric-phase contribution of heat flux. Finally, we propose an electronic experiment based on RC circuits to verify our theoretical predictions. © 2012 American Physical Society.
Wed, 23 May 2012 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/967152012-05-23T00:00:00Z
- Random matrix analysis of localization properties of gene coexpression networkhttps://scholarbank.nus.edu.sg/handle/10635/97750Title: Random matrix analysis of localization properties of gene coexpression network
Authors: Jalan, S.; Solymosi, N.; Vattay, G.; Li, B.
Abstract: We analyze gene coexpression network under the random matrix theory framework. The nearest-neighbor spacing distribution of the adjacency matrix of this network follows Gaussian orthogonal statistics of random matrix theory (RMT). Spectral rigidity test follows random matrix prediction for a certain range and deviates afterwards. Eigenvector analysis of the network using inverse participation ratio suggests that the statistics of bulk of the eigenvalues of network is consistent with those of the real symmetric random matrix, whereas few eigenvalues are localized. Based on these IPR calculations, we can divide eigenvalues in three sets: (a) The nondegenerate part that follows RMT. (b) The nondegenerate part, at both ends and at intermediate eigenvalues, which deviates from RMT and expected to contain information about important nodes in the network. (c) The degenerate part with zero eigenvalue, which fluctuates around RMT-predicted value. We identify nodes corresponding to the dominant modes of the corresponding eigenvectors and analyze their structural properties. © 2010 The American Physical Society.
Wed, 28 Apr 2010 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/977502010-04-28T00:00:00Z
- Electron transport in interacting hybrid mesoscopic systemshttps://scholarbank.nus.edu.sg/handle/10635/96410Title: Electron transport in interacting hybrid mesoscopic systems
Authors: Zeng, Z.Y.; Li, B.; Claro, F.
Abstract: A unified theory for the current through a mesoscopic region of interacting electrons connected to two leads which can be either ferromagnet or superconductor is presented, yielding Meir-Wingreen-type formulas when applied to specific circumstances. In such a formulation, the requirement of gauge invariance is satisfied automatically. Moreover, one can judge unambiguously what quantities can be measured in the transport experiment. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2003.
Wed, 01 Jan 2003 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/964102003-01-01T00:00:00Z
- Full control and manipulation of heat signatures: Cloaking, camouflage and thermal metamaterialshttps://scholarbank.nus.edu.sg/handle/10635/82387Title: Full control and manipulation of heat signatures: Cloaking, camouflage and thermal metamaterials
Authors: Han, T.; Bai, X.; Thong, J.T.L.; Li, B.; Qiu, C.-W.
Abstract: Thermal camouflage and cloaking can transform an actual heat signature into a pre-controlled one. A viable recipe for controlling and manipulating heat signatures using thermal metamaterials to empower cloaking and camouflage in heat conduction is demonstrated. The thermal signature of the object is thus metamorphosed and perceived as multiple targets with different geometries and compositions, with the original object cloaked. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Wed, 19 Mar 2014 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/823872014-03-19T00:00:00Z
- Simulation of crosstalk between small GTPase RhoA and EGFR-ERK signaling pathway via MEKK1https://scholarbank.nus.edu.sg/handle/10635/53170Title: Simulation of crosstalk between small GTPase RhoA and EGFR-ERK signaling pathway via MEKK1
Authors: Li, H.; Ung, C.Y.; Ma, X.H.; Li, B.W.; Low, B.C.; Cao, Z.W.; Chen, Y.Z.
Abstract: Motivation: Small GTPase RhoA regulates cell-cycle progression via several mechanisms. Apart from its actions via ROCK, RhoA has recently been found to activate a scaffold protein MEKK1 known to promote ERK activation. We examined whether RhoA can substantially affect ERK activity via this MEKK1-mediated crosstalk between RhoA and EGFR-ERK pathway. By extending the published EGFR-ERK simulation models represented by ordinary differential equations, we developed a simulation model that includes this crosstalk, which was validated with a number of experimental findings and published simulation results. Results: Our simulation suggested that, via this crosstalk, RhoA elevation substantially prolonged duration of ERK activation at both normal and reduced Ras levels. Our model suggests ERK may be activated in the absence of Ras. When Ras is overexpressed, RhoA elevation significantly prolongs duration of ERK activation but reduces the amount of active ERK partly due to competitive binding between ERK and RhoA to MEKK1. Our results indicated possible roles of RhoA in affecting ERK activities via MEKK1-mediated crosstalk, which seems to be supported by indications from several experimental studies that may also implicate the collective regulation of cell fate and progression of cancer and other diseases. © The Author 2008. Published by Oxford University Press. All rights reserved.
Thu, 01 Jan 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/531702009-01-01T00:00:00Z
- Thermal contraction in silicon nanowires at low temperatureshttps://scholarbank.nus.edu.sg/handle/10635/98352Title: Thermal contraction in silicon nanowires at low temperatures
Authors: Jiang, J.-W.; Wang, J.-S.; Li, B.
Abstract: The thermal expansion effect of silicon nanowires (SiNW) in [100], [110] and [111] directions with different sizes is theoretically investigated. At low temperatures, all SiNW studied exhibit a thermal contraction effect due to the lowest energy of the bending vibration mode which has a negative effect on the coefficient of thermal expansion (CTE). The CTE in [110] direction is distinctly larger than the other two growth directions because of the anisotropy of the bending mode in SiNW. Our study reveals that CTE decreases with an increase of the structure ratio γ = length/diameter, and is negative in the whole temperature range with γ = 1.3. © 2010 The Royal Society of Chemistry.
Mon, 01 Nov 2010 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/983522010-11-01T00:00:00Z
- Scaling of temperature-dependent thermal conductivities for one-dimensional nonlinear latticeshttps://scholarbank.nus.edu.sg/handle/10635/97859Title: Scaling of temperature-dependent thermal conductivities for one-dimensional nonlinear lattices
Authors: Li, N.; Li, B.
Abstract: In general nonlinear lattices, the existence of renormalized phonons due to the nonlinear interactions has been independently discovered by many research groups. Regarding these renormalized phonons as the energy carriers responsible for the heat transport, the scaling laws of temperature-dependent thermal conductivities of one-dimensional nonlinear lattices can be derived from the phenomenological effective phonon approach. For the paradigmatic nonlinear φ4 lattice, κ(T)T-1.35, which was numerically obtained more than a decade ago, can be well explained by the current approach. Most importantly, this approach is able to predict the scaling laws of temperature-dependent thermal conductivities of generalized nonlinear Klein-Gordon lattices. These theoretical predictions are compared by numerical simulations, and perfect agreements have been found. © 2013 American Physical Society.
Fri, 26 Apr 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/978592013-04-26T00:00:00Z
- Reduction of thermal conductivity of anharmonic latticeshttps://scholarbank.nus.edu.sg/handle/10635/97785Title: Reduction of thermal conductivity of anharmonic lattices
Authors: Wang, L.; Li, B.
Abstract: We study how to reduce thermal conductivity of anharmonic lattices. It is shown that high density of interface is an efficient way to get ultralow thermal conductivity, however, it does not work well when the density exceeds a certain value. This behavior is even clearer in harmonic lattices. The saturation of thermal conductivity in the case of disordered interface is similar to recent experiment results by Costescu in disordered multilayers of W/Al2 O3. © 2006 The American Physical Society.
Sun, 01 Jan 2006 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/977852006-01-01T00:00:00Z
- Nonlinearity enhanced interfacial thermal conductance and rectificationhttps://scholarbank.nus.edu.sg/handle/10635/97352Title: Nonlinearity enhanced interfacial thermal conductance and rectification
Authors: Zhang, L.; Thingna, J.; He, D.; Wang, J.-S.; Li, B.
Abstract: We study the nonlinear interfacial thermal transport across atomic junctions by the quantum self-consistent mean-field (QSCMF) theory based on the nonequilibrium Green's function approach; the QSCMF theory we propose is very precise and matches well with the exact results from quantum master equation. The nonlinearity at the interface is studied by effective temperature-dependent interfacial coupling calculated from the QSCMF theory. We find that nonlinearity can provide an extra channel for phonon transport in addition to the phonon scattering which usually blocks heat transfer. For weak linearly coupled interface, the nonlinearity can enhance the interfacial thermal transport; with increasing nonlinearity or temperature, the thermal conductance shows nonmonotonical behavior. The interfacial nonlinearity also induces thermal rectification, which depends on the mismatch of the two leads and also the interfacial linear coupling. © Copyright EPLA, 2013.
Sun, 01 Sep 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/973522013-09-01T00:00:00Z
- Reversal of thermal rectification in quantum systemshttps://scholarbank.nus.edu.sg/handle/10635/97820Title: Reversal of thermal rectification in quantum systems
Authors: Zhang, L.; Yan, Y.; Wu, C.-Q.; Wang, J.-S.; Li, B.
Abstract: We study thermal transport in anisotropic Heisenberg spin chains using the quantum master equation. It is found that thermal rectification changes sign when the external homogeneous magnetic field is varied. This reversal also occurs when the magnetic field becomes inhomogeneous. Moreover, we can tune the reversal of rectification by temperatures of the heat baths, the anisotropy, and size of the spin chains. © 2009 The American Physical Society.
Thu, 12 Nov 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/978202009-11-12T00:00:00Z
- Thermal conductivity of one-dimensional lattices with self-consistent heat baths: A heuristic derivationhttps://scholarbank.nus.edu.sg/handle/10635/98350Title: Thermal conductivity of one-dimensional lattices with self-consistent heat baths: A heuristic derivation
Authors: Li, N.; Li, B.
Abstract: We derive the thermal conductivities of one-dimensional harmonic and anharmonic lattices with selfconsistent heat baths from the single-mode relaxation time (SMRT) approximation. For harmonic lattice, we obtain the same result as previous works. However, our approach is heuristic and reveals phonon picture explicitly within the heat transport process. The results for harmonic and anharmonic lattices are compared with numerical calculations from Green-Kubo formula. The consistency between derivation and simulation strongly supports that effective (renormalized) phonons are energy carriers in anharmonic lattices although there exist some other excitations such as solitons and breathers. © 2009 The Physical Society of Japan.
Wed, 01 Apr 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/983502009-04-01T00:00:00Z
- The phonon Hall effect: Theory and applicationhttps://scholarbank.nus.edu.sg/handle/10635/98309Title: The phonon Hall effect: Theory and application
Authors: Zhang, L.; Ren, J.; Wang, J.-S.; Li, B.
Abstract: We present a systematic theory of the phonon Hall effect in a ballistic crystal lattice system, and apply it on the kagome lattice which is ubiquitous in various real materials. By proposing a proper second quantization for the non-Hermitian in the polarization-vector space, we obtain a new heat current density operator with two separate contributions: the normal velocity responsible for the longitudinal phonon transport, and the anomalous velocity manifesting itself as the Hall effect of transverse phonon transport. As exemplified in kagome lattices, our theory predicts that the direction of Hall conductivity at low magnetic field can be reversed by tuning the temperatures, which we hope can be verified by experiments in the future. Three phonon-Hall-conductivity singularities induced by phonon-band-topology change are discovered as well, which correspond to the degeneracies at three different symmetric center points, Γ, K, X, in the wavevector space of the kagome lattice. © 2011 IOP Publishing Ltd.
Wed, 03 Aug 2011 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/983092011-08-03T00:00:00Z
- Substrate coupling suppresses size dependence of thermal conductivity in supported graphenehttps://scholarbank.nus.edu.sg/handle/10635/98107Title: Substrate coupling suppresses size dependence of thermal conductivity in supported graphene
Authors: Chen, J.; Zhang, G.; Li, B.
Abstract: Thermal conductivity κ of both suspended and supported graphene has been studied by using molecular dynamics simulations. An obvious length dependence is observed in κ of suspended single-layer graphene (SLG), while κ of supported SLG is insensitive to the length. The simulation result of room temperature κ of supported SLG is in good agreement with the experimental value. In contrast to the decrease in κ induced by inter-layer interaction in suspended few-layer graphene (FLG), κ of supported FLG is found to increase rapidly with the layer thickness, reaching about 90% of that of bulk graphite at six layers, and eventually saturates at the thickness of 13.4 nm. More interestingly, unlike the remarkable substrate dependent κ in SLG, the effect of substrate on thermal transport is much weaker in FLG. The underlying physics is investigated and presented. This journal is © The Royal Society of Chemistry.
Mon, 21 Jan 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/981072013-01-21T00:00:00Z
- Interaction-induced quantum ratchet in a Bose-Einstein condensatehttps://scholarbank.nus.edu.sg/handle/10635/96952Title: Interaction-induced quantum ratchet in a Bose-Einstein condensate
Authors: Poletti, D.; Benenti, G.; Casati, G.; Li, B.
Abstract: We study the dynamics of a dilute Bose-Einstein condensate confined in a toroidal trap and exposed to a pair of periodically flashed optical lattices. We first prove that in the noninteracting case this system can present a quantum symmetry which forbids the ratchet effect classically expected. We then show how many-body atom-atom interactions, treated within the mean-field approximation, can break this quantum symmetry, thus generating directed transport. © 2007 The American Physical Society.
Fri, 24 Aug 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/969522007-08-24T00:00:00Z
- Interfacial thermal transport in atomic junctionshttps://scholarbank.nus.edu.sg/handle/10635/96967Title: Interfacial thermal transport in atomic junctions
Authors: Zhang, L.; Keblinski, P.; Wang, J.-S.; Li, B.
Abstract: We study ballistic interfacial thermal transport across atomic junctions. Exact expressions for phonon transmission coefficients are derived for thermal transport in one-junction and two-junction chains, and verified by numerical calculation based on a nonequilibrium Green's function method. For a single-junction case, we find that the phonon transmission coefficient typically decreases monotonically with increasing freqency. However, in the range between the point of equal frequency spectrum and that of equal acoustic impedance, it first increases then decreases, which explains why the Kapitza resistance calculated from the acoustic mismatch model is far larger than the experimental values at low temperatures. The junction thermal conductance reaches a maximum when the interfacial coupling equals the harmonic average of the spring constants of the two semi-infinite chains. For three-dimensional junctions, in the weak coupling limit, we find that the conductance is proportional to the square of the interfacial coupling, while for a intermediate coupling strength the conductance is approximately proportional to the interfacial coupling strength. For two-junction chains, the transmission coefficient oscillates with the frequency due to interference effects. The oscillations between the two envelope lines can be understood analytically, thus providing guidelines for designing phonon frequency filters. © 2011 American Physical Society.
Fri, 11 Feb 2011 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/969672011-02-11T00:00:00Z
- Homogeneous thermal cloak with constant conductivity and tunable heat localizationhttps://scholarbank.nus.edu.sg/handle/10635/50940Title: Homogeneous thermal cloak with constant conductivity and tunable heat localization
Authors: Han, T.; Yuan, T.; Li, B.; Qiu, C.-W.
Abstract: Invisible cloak has long captivated the popular conjecture and attracted intensive research in various communities of wave dynamics, e.g., optics, electromagnetics, acoustics, etc. However, their inhomogeneous and extreme parameters imposed by transformation-optic method will usually require challenging realization with metamaterials, resulting in narrow bandwidth, loss, polarization-dependence, etc. In this paper, we demonstrate that thermodynamic cloak can be achieved with homogeneous and finite conductivity only employing naturally available materials. It is demonstrated that the thermal localization inside the coating layer can be tuned and controlled robustly by anisotropy, which enables an incomplete cloak to function perfectly. Practical realization of such homogeneous thermal cloak has been suggested by using two naturally occurring conductive materials, which provides an unprecedentedly plausible way to flexibly realize thermal cloak and manipulate heat flow with phonons.
Tue, 01 Jan 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/509402013-01-01T00:00:00Z
- Effective phonons in anharmonic lattices: Anomalous vs. normal heat conductionhttps://scholarbank.nus.edu.sg/handle/10635/96354Title: Effective phonons in anharmonic lattices: Anomalous vs. normal heat conduction
Authors: Li, N.; Tong, P.; Li, B.
Abstract: We study heat conduction in one-dimensional (1D) anharmonic lattices analytically and numerically by using an effective phonon theory. It is found that every effective phonon mode oscillates quasi-periodically. By weighting the power spectrum of the total heat flux in the Debye formula, we obtain a unified formalism that can explain anomalous heat conduction in momentum conserved lattices without on-site potential and normal heat conduction in lattices with on-site potential. Our results agree very well with numerical ones for existing models such as the Fermi-Pasta-Ulam model, the Prenkel-Kontorova model and the Φ4 model etc. © EDP Sciences.
Sat, 01 Jul 2006 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/963542006-07-01T00:00:00Z
- Diameter-dependent thermal transport in individual ZnO nanowires and its correlation with surface coating and defectshttps://scholarbank.nus.edu.sg/handle/10635/82152Title: Diameter-dependent thermal transport in individual ZnO nanowires and its correlation with surface coating and defects
Authors: Bui, C.T.; Xie, R.; Zheng, M.; Zhang, Q.; Sow, C.H.; Li, B.; Thong, J.T.L.
Abstract: A systematic study of the thermal transport properties of individual single-crystal zinc oxide (ZnO) nanowires (NWs) with diameters in the range of ∼50-210 nm is presented. The thermal conductivity of the NWs is found to be dramatically reduced by at least an order of magnitude compared to bulk values, due to enhanced phonon-boundary scattering with a reduction in sample size. While the conventional phonon transport model can qualitatively explain the temperature dependence, it fails to account for the diameter dependence. An empirical relationship for assessing diameter-dependent thermal properties is observed, which shows an approximately linear dependence of the thermal conductivity on the cross-sectional area of the NWs in the measured diameter range. Furthermore, it is found that an amorphous-carbon layer coating on the NWs does not perturb the thermal properties of the NW cores, whereas 30 keV Ga + ion irradiation at low dose (∼4 ×10 14 cm -2) leads to a remarkable reduction of the thermal conductivity of the ZnO NWs. Thermal transport properties of individual zinc oxide nanowires are characterized using a suspended micro-electro-thermal device. It is found that the thermal conductivities of the nanowires are dramatically reduced by at least one order of magnitude compared to bulk values. An empirical relationship for assessing diameter-dependent thermal properties is observed, which shows an approximately linear dependence of the thermal conductivity on the cross-section area of the nanowires in the measured diameter range. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Mon, 12 Mar 2012 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/821522012-03-12T00:00:00Z
- Shuttling heat across one-dimensional homogenous nonlinear lattices with a Brownian heat motorhttps://scholarbank.nus.edu.sg/handle/10635/97915Title: Shuttling heat across one-dimensional homogenous nonlinear lattices with a Brownian heat motor
Authors: Li, N.; Zhan, F.; Hänggi, P.; Li, B.
Abstract: We investigate directed thermal heat flux across one-dimensional homogenous nonlinear lattices when no net thermal bias is present on average. A nonlinear lattice of Fermi-Pasta-Ulam-type or Lennard-Jones-type system is connected at both ends to thermal baths which are held at the same temperature on temporal average. We study two different modulations of the heat bath temperatures, namely: (i) a symmetric, harmonic ac driving of temperature of one heat bath only and (ii) a harmonic mixing drive of temperature acting on both heat baths. While for case (i) an adiabatic result for the net heat transport can be derived in terms of the temperature-dependent heat conductivity of the nonlinear lattice a similar such transport approach fails for the harmonic mixing case (ii). Then, for case (ii), not even the sign of the resulting Brownian motion induced heat flux can be predicted a priori. A nonvanishing heat flux (including a nonadiabatic reversal of flux) is detected which is the result of an induced dynamical symmetry breaking mechanism in conjunction with the nonlinearity of the lattice dynamics. Computer simulations demonstrate that the heat flux is robust against an increase of lattice sizes. The observed ratchet effect for such directed heat currents is quite sizable for our studied class of homogenous nonlinear lattice structures, thereby making this setup accessible for experimental implementation and verification. © 2009 The American Physical Society.
Thu, 06 Aug 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/979152009-08-06T00:00:00Z
- Large negative differential resistance in a molecular junction of carbon nanotube and anthracenehttps://scholarbank.nus.edu.sg/handle/10635/97041Title: Large negative differential resistance in a molecular junction of carbon nanotube and anthracene
Authors: Xu, Y.; Zhang, G.; Li, B.
Abstract: We propose a novel molecular junction with single walled carbon nanotube (SWNT) as electrodes bridged by an anthracene molecule. It is found that when the coupling between the molecule and the SWNT is noncovalent, the current-voltage (I-V) curve shows a striking nonlinear feature and a large negative differential resistance (NDR) at small bias. While in covalent adsorption site, the I- V curve behaves nearly linear. Theoretical studies based on the nonequilibrium Green's function method demonstrate that mechanism of the NDR is due to the narrow features of the local density of states (LDOS) of the SWNT as well as the alignment between the peak of LDOS of the electrodes and the molecular energy levels.© 2008 American Chemical Society.
Thu, 25 Dec 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/970412008-12-25T00:00:00Z
- Ratchet-induced matter-wave transport and soliton collisions in Bose-Einstein condensateshttps://scholarbank.nus.edu.sg/handle/10635/97758Title: Ratchet-induced matter-wave transport and soliton collisions in Bose-Einstein condensates
Authors: Poletti, D.; Ostrovskaya, E.A.; Alexander, T.J.; Li, B.; Kivshar, Y.S.
Abstract: We study the dynamics of bright matter-wave solitons in a Bose-Einstein condensate with negative scattering length under the influence of a time-periodic ratchet potential. The potential is formed by a one-dimensional bichromatic optical lattice which flashes on and off so that the time average of its amplitude vanishes. Due to the broken space and time-reversal symmetries of the potential, the soliton is transported with a nonzero average velocity. By employing the non-dissipative mean-field model for the matter waves, we study the dependence of the transport velocity on the initial state of the soliton and show how the properties of the individual localized states affect the outcome of their collisions. A useful insight into the transport properties is provided by Hamiltonian theory for the mean field, which treats the extended matter-wave excitation as an effective classical particle. © 2008 Elsevier B.V. All rights reserved.
Wed, 15 Jul 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/977582009-07-15T00:00:00Z