ScholarBank@NUShttps://scholarbank.nus.edu.sgThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Tue, 30 May 2023 11:47:08 GMT2023-05-30T11:47:08Z502191- 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
- 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
- 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
- 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
- Experimental evidence of wave chaos from a double slit experiment with water surface waveshttps://scholarbank.nus.edu.sg/handle/10635/96555Title: Experimental evidence of wave chaos from a double slit experiment with water surface waves
Authors: Tang, Y.; Shen, Y.; Yang, J.; Liu, X.; Zi, J.; Li, B.
Abstract: In this paper, we report experimental evidence of wave chaos using the double slit water surface wave experiment. We demonstrate that classical dynamics of a domain manifests itself in the interference patterns after the diffraction behind the double slit. For a domain whose classical dynamics is integrable clear interference fringes can be observed behind the double slits; for a domain whose classical dynamics is chaotic, however, interference fringes can totally disappear. Our experimental results clearly demonstrate that the centuries-old double slit experiment can render an excellent tool to observe the manifestations of wave chaos. © 2008 The American Physical Society.
Wed, 01 Oct 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/965552008-10-01T00:00:00Z
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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: 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
- 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
- Anomalous heat conduction and anomalous diffusion in low dimensional nanoscale systemshttps://scholarbank.nus.edu.sg/handle/10635/95799Title: Anomalous heat conduction and anomalous diffusion in low dimensional nanoscale systems
Authors: Liu, S.; Xu, X.F.; Xie, R.G.; Zhang, G.; Li, B.W.
Abstract: Heat conduction is an important energy transport process in nature. Phonon is the major energy carrier for heat in semiconductors and dielectric materials. In analogy to Ohm's law of electrical conduction, Fourier's law is the fundamental law of heat conduction in solids. Although Fourier's law has received great success in describing macroscopic heat conduction in the past two hundred years, its validity in low dimensional systems is still an open question. Here we give a brief review of the recent developments in experimental, theoretical and numerical studies of heat conduction in low dimensional systems, including lattice models and low dimensional nanostructures such as nanowires, nanotubes and graphene. We will demonstrate that phonons transport in low dimensional systems superdiffusively, which leads to a size dependent thermal conductivity. In other words, Fourier's law is not applicable in low dimensional structures. © 2012 EDP Sciences, Società Italiana di Fisica, Springer-Verlag.
Mon, 01 Oct 2012 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/957992012-10-01T00:00:00Z
- Anomalous heat diffusionhttps://scholarbank.nus.edu.sg/handle/10635/95800Title: Anomalous heat diffusion
Authors: Liu, S.; Hänggi, P.; Li, N.; Ren, J.; Li, B.
Abstract: Consider anomalous energy spread in solid phases, i.e., Δx2(t)≡∫(x-x)2ρE(x,t)dx tβ, as induced by a small initial excess energy perturbation distribution ρE(x,t=0) away from equilibrium. The second derivative of this variance of the nonequilibrium excess energy distribution is shown to rigorously obey the intriguing relation d2Δx2(t)/dt2=2CJJ(t)/(kBT2c), where CJJ(t) equals the thermal equilibrium total heat flux autocorrelation function and c is the specific volumetric heat capacity. Its integral assumes a time-local Helfand-like relation. Given that the averaged nonequilibrium heat flux is governed by an anomalous heat conductivity, the energy diffusion scaling determines a corresponding anomalous thermal conductivity scaling behavior. © 2014 American Physical Society.
Tue, 28 Jan 2014 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/958002014-01-28T00:00:00Z
- Boosting thermoelectric efficiency using time-dependent controlhttps://scholarbank.nus.edu.sg/handle/10635/175981Title: Boosting thermoelectric efficiency using time-dependent control
Authors: Zhou, H; Thingna, J; H„nggi, P; Wang, J.-S; Li, B
Abstract: Thermoelectric efficiency is defined as the ratio of power delivered to the load of a device to the rate of heat flow from the source. Till date, it has been studied in presence of thermodynamic constraints set by the Onsager reciprocal relation and the second law of thermodynamics that severely bottleneck the thermoelectric efficiency. In this study, we propose a pathway to bypass these constraints using a time-dependent control and present a theoretical framework to study dynamic thermoelectric transport in the far from equilibrium regime. The presence of a control yields the sought after substantial efficiency enhancement and importantly a significant amount of power supplied by the control is utilised to convert the wasted-heat energy into useful-electric energy. Our findings are robust against nonlinear interactions and suggest that external time-dependent forcing, which can be incorporated with existing devices, provides a beneficial scheme to boost thermoelectric efficiency.
Thu, 01 Jan 2015 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1759812015-01-01T00:00:00Z
- Gallium ion implantation greatly reduces thermal conductivity and enhances electronic one of ZnO nanowireshttps://scholarbank.nus.edu.sg/handle/10635/174656Title: Gallium ion implantation greatly reduces thermal conductivity and enhances electronic one of ZnO nanowires
Authors: Xia, M; Cheng, Z; Han, J; Zheng, M; Sow, C.-H; Thong, J.T.L; Zhang, S; Li, B
Abstract: The electrical and thermal conductivities are measured for individual zinc oxide (ZnO) nanowires with and without gallium ion (Ga+) implantation at room temperature. Our results show that Ga+ implantation enhances electrical conductivity by one order of magnitude from 1.01 × 10 3 Ω-1m-1 to 1.46 × 104 Ω-1m-1 and reduces its thermal conductivity by one order of magnitude from 12.7 Wm-1K-1 to 1.22 Wm -1K-1 for ZnO nanowires of 100 nm in diameter. The measured thermal conductivities are in good agreement with those in theoretical simulation. The increase of electrical conductivity origins in electron donor doping by Ga+ implantation and the decrease of thermal conductivity is due to the longitudinal and transverse acoustic phonons scattering by Ga + point scattering. For pristine ZnO nanowires, the thermal conductivity decreases only two times when its diameter reduces from 100 nm to 46 nm. Therefore, Ga+-implantation may be a more effective method than diameter reduction in improving thermoelectric performance. © 2014 Author(s).
Wed, 01 Jan 2014 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1746562014-01-01T00:00:00Z
- Manipulating acoustic wavefront by inhomogeneous impedance and steerable extraordinary reflectionhttps://scholarbank.nus.edu.sg/handle/10635/174588Title: Manipulating acoustic wavefront by inhomogeneous impedance and steerable extraordinary reflection
Authors: Zhao J.; Li B.; Chen Z.; Qiu C.-W.
Abstract: We unveil the connection between the acoustic impedance along a flat surface and the reflected acoustic wavefront, in order to empower a wide wariety of novel applications in acoustic community. Our designed flat surface can generate double reflections: the ordinary reflection and the extraordinary one whose wavefront is manipulated by the proposed impedance-governed generalized Snell's law of reflection (IGSL). IGSL is based on Green's function and integral equation, instead of Fermat's principle for optical wavefront manipulation. Remarkably, via the adjustment of the designed specific acoustic impedance, extraordinary reflection can be steered for unprecedented acoustic wavefront while that ordinary reflection can be surprisingly switched on or off. The realization of the complex discontinuity of the impedance surface has been proposed using Helmholtz resonators.
Tue, 01 Jan 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1745882013-01-01T00:00:00Z
- 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
- Anomalous heat conduction and anomalous diffusion in nonlinear lattices, single walled nanotubes, and billiard gas channelshttps://scholarbank.nus.edu.sg/handle/10635/116229Title: Anomalous heat conduction and anomalous diffusion in nonlinear lattices, single walled nanotubes, and billiard gas channels
Authors: Li, B.; Wang, J.; Wang, L.; Zhang, G.
Abstract: We study anomalous heat conduction and anomalous diffusion in low-dimensional systems ranging from nonlinear lattices, single walled carbon nanotubes, to billiard gas channels. We find that in all discussed systems, the anomalous heat conductivity can be connected with the anomalous diffusion, namely, if energy diffusion is o 2(t)=2Dt α (0 < α ≤ 2), then the thermal conductivity can be expressed in terms of the system size L as K=cL β with β=2-2/α. This result predicts that a normal diffusion (a=l) implies a normal heat conduction obeying the Fourier law (β=0), a superdiffusion (α > 1) implies an anomalous heat conduction with a divergent thermal conductivity (β>0), and more interestingly, a subdiffusion (α < 1) implies an anomalous heat conduction with a convergent thermal conductivity (β < 0), consequently, the system is a thermal insulator in the thermodynamic limit. Existing numerical data support our theoretical prediction. © 2005 American Institute of Physics.
Sat, 01 Jan 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1162292005-01-01T00:00:00Z
- 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
- How does folding modulate thermal conductivity of graphene?https://scholarbank.nus.edu.sg/handle/10635/96835Title: How does folding modulate thermal conductivity of graphene?
Authors: Yang, N.; Ni, X.; Jiang, J.-W.; Li, B.
Abstract: We study thermal transport in folded graphene nanoribbons using molecular dynamics simulations and the non-equilibrium Green's function method. It is found that the thermal conductivity of flat graphene nanoribbons can be modulated by folding and changing interlayer couplings. The analysis of transmission reveals that the reduction of thermal conductivity is due to scattering of low frequency phonons by the folds. Our results suggest that folding can be utilized in the modulation of thermal transport properties in graphene and other two dimensional materials. © 2012 American Institute of Physics.
Mon, 27 Feb 2012 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/968352012-02-27T00:00:00Z
- 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
- Parameter-dependent thermal conductivity of one-dimensional 4 latticehttps://scholarbank.nus.edu.sg/handle/10635/97487Title: Parameter-dependent thermal conductivity of one-dimensional 4 lattice
Authors: Li, N.; Li, B.
Abstract: We examine the thermal conductivity of a one-dimensional 4 lattice with strong on-site harmonic potential. The expression for the thermal conductivity in terms of different parameters is derived from the effective phonon theory. Numerical calculations using nonequilibrium molecular dynamics are compared with the predictions of the effective phonon theory and the theory of the Peierls-Boltzmann transport equation. It is found that the numerical results are consistent with the prediction of the effective phonon theory in the intermediate parameter range and approach the predictions of Peierls-Boltzmann transport theory in the strongly pinned limit. © 2007 The American Physical Society.
Fri, 13 Jul 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/974872007-07-13T00:00:00Z
- Effects of lithium insertion on thermal conductivity of silicon nanowireshttps://scholarbank.nus.edu.sg/handle/10635/127196Title: Effects of lithium insertion on thermal conductivity of silicon nanowires
Authors: Xu, Wen; Zhang, Gang; Li, Baowen
Thu, 01 Jan 2015 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1271962015-01-01T00:00:00Z
- Reduction of thermal conductivity by nanoscale 3D phononic crystalhttps://scholarbank.nus.edu.sg/handle/10635/97784Title: Reduction of thermal conductivity by nanoscale 3D phononic crystal
Authors: Yang, L.; Yang, N.; Li, B.
Abstract: We studied how the period length and the mass ratio affect the thermal conductivity of isotopic nanoscale three-dimensional (3D) phononic crystal of Si. Simulation results by equilibrium molecular dynamics show isotopic nanoscale 3D phononic crystals can significantly reduce the thermal conductivity of bulk Si at high temperature (1000â.K), which leads to a larger ZT than unity. The thermal conductivity decreases as the period length and mass ratio increases. The phonon dispersion curves show an obvious decrease of group velocities in 3D phononic crystals. The phonon's localization and band gap is also clearly observed in spectra of normalized inverse participation ratio in nanoscale 3D phononic crystal.
Tue, 01 Jan 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/977842013-01-01T00:00:00Z
- Thermal rectification and negative differential thermal resistance in lattices with mass gradienthttps://scholarbank.nus.edu.sg/handle/10635/98362Title: Thermal rectification and negative differential thermal resistance in lattices with mass gradient
Authors: Yang, N.; Li, N.; Wang, L.; Li, B.
Abstract: We study thermal properties of one-dimensional (1D) harmonic and anharmonic lattices with a mass gradient. It is found that a temperature gradient can be built up in the 1D harmonic lattice with a mass gradient due to the existence of gradons. The heat flow is asymmetric in anharmonic lattices with a mass gradient. Moreover, in a certain temperature region, negative differential thermal resistance is observed. Possible applications in constructing thermal rectifiers and thermal transistors by using the graded material are discussed. © 2007 The American Physical Society.
Tue, 24 Jul 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/983622007-07-24T00:00:00Z
- Thermal conductivity of nanotubes revisited: Effects of chirality, isotope impurity, tube length, and temperaturehttps://scholarbank.nus.edu.sg/handle/10635/98349Title: Thermal conductivity of nanotubes revisited: Effects of chirality, isotope impurity, tube length, and temperature
Authors: Zhang, G.; Li, B.
Abstract: We study the dependence of the thermal conductivity of single-walled nanotubes on chirality, isotope impurity, tube length, and temperature by nonequilibrium molecular-dynamics method with accurate potentials. It is found that, contrary to electronic conductivity, the thermal conductivity is insensitive to the chirality. The isotope impurity, however, can reduce the thermal conductivity up to 60% and change the temperature dependence behavior. We also found that the tube length dependence of thermal conductivity is different for nanotubes of different radii at different temperatures. © 2005 American Institute of Physics.
Thu, 15 Sep 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/983492005-09-15T00:00:00Z
- Control of heat transport in quantum spin systemshttps://scholarbank.nus.edu.sg/handle/10635/96077Title: Control of heat transport in quantum spin systems
Authors: Yan, Y.; Wu, C.-Q.; Li, B.
Abstract: We study heat transport in quantum spin systems analytically and numerically. First, we demonstrate that heat current through a two-level quantum spin system can be modulated from zero to a finite value by tuning a magnetic field. Second, we show that a spin system, consisting of two dissimilar parts-one is gapped and the other is gapless-exhibits current rectification and negative differential thermal resistance. Possible experimental realizations by using molecular junctions or magnetic materials are discussed. © 2009 The American Physical Society.
Mon, 05 Jan 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/960772009-01-05T00:00:00Z
- Phonon coherent resonance and its effect on thermal transport in core-shell nanowireshttps://scholarbank.nus.edu.sg/handle/10635/97524Title: Phonon coherent resonance and its effect on thermal transport in core-shell nanowires
Authors: Chen, J.; Zhang, G.; Li, B.
Abstract: We study heat current autocorrelation function and thermal conductivity in core-shell nanowires by using molecular dynamics simulations. Interestingly, a remarkable oscillation effect in heat current autocorrelation function is observed in core-shell NWs, while the same effect is absent in pure silicon nanowires, nanotube structures, and random doped nanowires. Detailed characterizations of the oscillation signal reveal that this intriguing oscillation is caused by the coherent resonance effect of the transverse and longitudinal phonon modes. This phonon resonance results in the localization of the longitudinal modes, which leads to the reduction of thermal conductivity in core-shell nanowires. Our study reveals that a coherent mechanism can be used to tune thermal conductivity in core-shell nanowires. © 2011 American Institute of Physics.
Wed, 14 Sep 2011 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/975242011-09-14T00:00:00Z
- Heat current limiter and constant heat current sourcehttps://scholarbank.nus.edu.sg/handle/10635/96770Title: Heat current limiter and constant heat current source
Authors: Wu, J.; Wang, L.; Li, B.
Abstract: Current limiters and constant current sources, which play important roles in electronic circuits, have been built up for many decades. Their thermal counterparts, heat current limiters and constant heat current sources, are still not available yet. By combining two typical nonlinear lattices, the Frenkel-Kontorova (FK) lattice and a coupled rotator lattice, together, we present by numerical simulation a model that displays complete negative differential thermal resistance (NDTR). Namely, in a wide regime, the heat current that flows through this model is always a decreasing function of the temperature drop applied to it, no matter whether the change in the temperature drop is due to a change in the high or the low temperature. We show that, upon being properly set up, a complete NDTR can work as either a heat current limiter or a constant heat current source. © 2012 American Physical Society.
Mon, 11 Jun 2012 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/967702012-06-11T00:00:00Z
- 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
- Thermal transport across metal-insulator interface via electron-phonon interactionhttps://scholarbank.nus.edu.sg/handle/10635/98373Title: Thermal transport across metal-insulator interface via electron-phonon interaction
Authors: Zhang, L.; Lü, J.-T.; Wang, J.-S.; Li, B.
Abstract: The thermal transport across a metal-insulator interface can be characterized by electron-phonon interaction through which an electron lead is coupled to a phonon lead if phonon-phonon coupling at the interface is very weak. We investigate the thermal conductance and rectification between the electron part and the phonon part using the nonequilibrium Green's function method. It is found that the thermal conductance has a nonmonotonic behavior as a function of average temperature or the coupling strength between the phonon leads in the metal part and the insulator part. The metal-insulator interface shows a clear thermal rectification effect, which can be reversed by a change in average temperature or the electron-phonon coupling. © 2013 IOP Publishing Ltd.
Wed, 06 Nov 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/983732013-11-06T00:00:00Z
- A universal expression of band gap for silicon nanowires of different cross-section geometrieshttps://scholarbank.nus.edu.sg/handle/10635/95700Title: A universal expression of band gap for silicon nanowires of different cross-section geometries
Authors: Yao, D.; Zhang, G.; Li, B.
Abstract: We use the first-principles tight binding method to investigate the electronic structure and band gap of [110] oriented hydrogen-passivated silicon nanowires (SiNWs) of different cross-sectional geometries. A quantitative universal band gap expression for [110] SiNWs is obtained, which shows a linear dependence of band gap on the surface area to volume ratio (SVR), and it is independent of the cross-sectional geometry. In contrast to the ambiguity in the definition of the SiNW transverse dimension, using of SVR has the advantage to readily predict band gap for SiNWs with any cross-sectional shapes. Our results demonstrate that the SVR is an ideal "gauge" to describe the band gap of SiNWs. © 2008 American Chemical Society.
Mon, 01 Dec 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/957002008-12-01T00:00:00Z
- 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
- Anomalous thermal transport in disordered harmonic chains and carbon nanotubeshttps://scholarbank.nus.edu.sg/handle/10635/95806Title: Anomalous thermal transport in disordered harmonic chains and carbon nanotubes
Authors: Ni, X.; Leek, M.L.; Wang, J.-S.; Feng, Y.P.; Li, B.
Abstract: We report the coherent potential approximation method of treating quantum thermal transport properties of nanoscale systems with mass disorder. Instead of massive efforts required in brute-force calculations, configuration averaging of disordered systems can be efficiently handled in a self-consistent manner by setting up the phonon version of nonequilibrium vertex correction theory. The accuracy of the method is verified by comparing with the exact results and Monte Carlo experiments in one-dimensional atomic chains. Results obtained for disordered harmonic chains and carbon nanotubes provide evidence of anomalous thermal transport in such systems. We also observe crossover in the transport where phonon scattering by disorder becomes important. Our results show that disorder plays a role in thermal conductance reduction. © 2011 American Physical Society.
Fri, 21 Jan 2011 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/958062011-01-21T00:00:00Z
- Interface thermal resistance between dissimilar anharmonic latticeshttps://scholarbank.nus.edu.sg/handle/10635/115157Title: Interface thermal resistance between dissimilar anharmonic lattices
Authors: Li, B.; Lan, J.; Wang, L.
Abstract: We study interface thermal resistance (ITR) in a system consisting of two dissimilar anharmonic lattices exemplified by the Fermi-Pasta-Ulam and Frenkel-Kontorova models. It is found that the ITR is asymmetric; namely, it depends on how the temperature gradient is applied. The dependence of the ITR on the coupling constant, temperature, temperature difference, and system size is studied. Possible applications in nanoscale heat management and control are discussed. © 2005 The American Physical Society.
Fri, 02 Sep 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1151572005-09-02T00:00:00Z
- Current behavior of a quantum Hamiltonian ratchet in resonancehttps://scholarbank.nus.edu.sg/handle/10635/96140Title: Current behavior of a quantum Hamiltonian ratchet in resonance
Authors: Poletti, D.; Carlo, G.G.; Li, B.
Abstract: We investigate the ratchet current that appears in a kicked Hamiltonian system when the period of the kicks corresponds to the regime of quantum resonance. In the classical analog, a spatial-temporal symmetry should be broken to obtain a net directed current. It was recently discovered that in quantum resonance the temporal symmetry can be kept, and we prove that breaking the spatial symmetry is a necessary condition to find this effect. Moreover, we show numerically and analytically how the direction of the motion is dramatically influenced by the strength of the kicking potential and the value of the period. By increasing the strength of the interaction this direction changes periodically, providing us with un-expected source of current reversals in this quantum model. These reversals depend on the kicking period also, though this behavior is theoretically more difficult to analyze. Finally, we generalize the discussion to the case of a nonuniform initial condition. © 2007 The American Physical Society.
Mon, 01 Jan 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/961402007-01-01T00:00:00Z
- 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
- Classical heat transport in anharmonic molecular junctions: Exact solutionshttps://scholarbank.nus.edu.sg/handle/10635/95994Title: Classical heat transport in anharmonic molecular junctions: Exact solutions
Authors: Liu, S.; Agarwalla, B.K.; Wang, J.-S.; Li, B.
Abstract: We study full counting statistics for classical heat transport through anharmonic or nonlinear molecular junctions formed by interacting oscillators. An analytical result of the steady-state heat flux for an overdamped anharmonic junction with arbitrary temperature bias is obtained. It is found that the thermal conductance can be expressed in terms of a temperature-dependent effective force constant. The role of anharmonicity is identified. We also give the general formula for the second cumulant of heat in steady state, as well as the average geometric heat flux when two system parameters are modulated adiabatically. We present an anharmonic example for which all cumulants for heat can be obtained exactly. For a bounded single oscillator model with mass we found that the cumulants are independent of the nonlinear potential. © 2013 American Physical Society.
Tue, 19 Feb 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/959942013-02-19T00:00:00Z
- Local and nonlocal entanglement for quasiparticle pairs induced by Andreev reflectionhttps://scholarbank.nus.edu.sg/handle/10635/97079Title: Local and nonlocal entanglement for quasiparticle pairs induced by Andreev reflection
Authors: Zeng, Z.Y.; Zhou, L.; Hong, J.; Li, B.
Abstract: We investigate local and nonlocal entanglement of particle pairs induced by direct and crossed Andreev reflections at the interfaces between a superconductor and two normal conductors. It is shown theoretically that both local and nonlocal entanglement can be quantified by concurrence and detected from the violation of a Bell inequality of spin current correlators, which are determined only by normal reflection and Andreev reflection eigenvalues. There exists a one-to-one correspondence between the concurrence and the maximal Bell-CHSH parameter in the tunneling limit. © 2006 The American Physical Society.
Sun, 01 Jan 2006 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/970792006-01-01T00:00:00Z