ScholarBank@NUShttps://scholarbank.nus.edu.sgThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Mon, 22 Jul 2024 10:21:51 GMT2024-07-22T10:21:51Z50141- Zero modes & fractional charge in bilayer graphenehttps://scholarbank.nus.edu.sg/handle/10635/72222Title: Zero modes & fractional charge in bilayer graphene
Authors: Martinez, J.C.; Jalil, M.B.A.; Tan, S.G.
Abstract: We obtain zero modes of bilayer graphene (BG) with a kink potential. Such solutions have topologically robust properties. We study fractional charge in BG with the trigonal interaction and discuss possible detection. © 2011 American Institute of Physics.
Sat, 01 Jan 2011 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/722222011-01-01T00:00:00Z
- Theory of giant Faraday rotation and Goos-Hänchen shift in graphenehttps://scholarbank.nus.edu.sg/handle/10635/57648Title: Theory of giant Faraday rotation and Goos-Hänchen shift in graphene
Authors: Martinez, J.C.; Jalil, M.B.A.
Abstract: We give a quantum formulation of the recently observed giant Faraday rotation (FR) in monolayer graphene (Crassee I., Nat. Phys., 7 (2011) 48) which incorporates graphene's anomalous Hall effect and the resonant interplay between Landau levels and Floquet sidebands in the limit of large Fermi energy. The same formalism is then used to discuss the Goos-Hänchen (GH) shift at the interface of two media of different permittivity, with graphene at their interface. This last feature introduces current into the electromagnetic boundary conditions. For the s-polarization case, the presence of the graphene-induced surface charge causes a much larger GH shift than without charge, and its usual monotonic behavior is altered. In the p-polarization case, surface charge and current may alter the conventional GH shift in opposite ways. We predict new phenomena such as minimum GH shift and a lateral broadening of the reflected beam, all of which should be observable with current experimental capabilities. © Europhysics Letters Association 2011.
Sat, 01 Jan 2011 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/576482011-01-01T00:00:00Z
- Theory of dark optical solitonshttps://scholarbank.nus.edu.sg/handle/10635/57647Title: Theory of dark optical solitons
Authors: Martinez, J.C.; Shutler, P.M.E.; Toon, A.
Abstract: We study the quantum fluctuations about a dark soliton generated in a photon fluid confined in a Kerr-effect nonlinear microcavity. Semiclassical quantization imposes quantization conditions that lend a particle interpretation to the fluctuations. A Bogoliubov-de Gennes analysis complements this view by yielding the single-particle energies and wave functions. The zero modes are found to correspond to the background while the scattering solutions to the notch. We compute the mass associated with the soliton. © 2008 American Institute of Physics.
Tue, 01 Jan 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/576472008-01-01T00:00:00Z
- Tuning the Casimir force via modification of interface properties of three-dimensional topological insulatorshttps://scholarbank.nus.edu.sg/handle/10635/57723Title: Tuning the Casimir force via modification of interface properties of three-dimensional topological insulators
Authors: Martinez, J.C.; Jalil, M.B.A.
Abstract: The axion coupling in topological insulators (TI), which couples electric polarization (magnetization) with the magnetic (electric) field, is known to support a small-distance Casimir repulsion and a large-distance Casimir attraction with a zero-force stable equilibrium between TI plates. By enhancing the reflection properties of the TI interface through mirrors that introduce multiple reflections, we show that it is possible to maintain these trends while tuning the position of the zero-force point and its binding energy: the former by an order of magnitude and latter by over four orders. Moreover, surface charge on the TI allows for intermediate tuning of the zero-force point between coarse settings determined by the axion coupling. © 2013 AIP Publishing LLC.
Tue, 01 Jan 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/577232013-01-01T00:00:00Z
- Semiclassical quantization of the one- and two-kink dark solitonshttps://scholarbank.nus.edu.sg/handle/10635/57376Title: Semiclassical quantization of the one- and two-kink dark solitons
Authors: Martinez, J.C.; Jalil, M.B.A.
Abstract: Drawing from an analogy with a linear particle-chain model, we develop a picture of the dark optical soliton as a composite of a background and notch each enjoying a certain degree of independence. The semiclassical quantization procedure of Dashen [Phys. Rev. D 11, 3424 (1975)] is modified to allow for the separate quantization of these two entities. We apply our results to the one-kink and two-kink dark solitons. For both we find that the fluctuations about the notch can be understood as a bound state of bosons held by an attractive delta potential while the background fluctuations are seen as an ensemble of oscillators with a slightly repulsive interaction. We show that the collision effects are small for the two-kink soliton. The quantum numbers emerging from this analysis are interpreted in terms of the number of particles. Moreover, the topological character of the dark soliton also appears naturally in our description. We speculate on the possibility of fractional quantum numbers and derive the repulsive interaction of two dark solitons from the framework developed for the two-kink soliton. © 2009 The American Physical Society.
Wed, 01 Apr 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/573762009-04-01T00:00:00Z
- Pseudospin filter for graphene via laser irradiationhttps://scholarbank.nus.edu.sg/handle/10635/57152Title: Pseudospin filter for graphene via laser irradiation
Authors: Martinez, J.C.; Jalil, M.B.A.; Tan, S.G.
Abstract: We study graphene monolayer charge carriers irradiated by an electromagnetic vortex. From this, two scenarios are envisaged: canonical oscillator coherent states, which form for large particle numbers and from which a sublattice filter can be constructed, and pair-coherent states, which emerge when the carrier velocity is much less than the Fermi velocity and which can exhibit nonclassical properties. The first should be useful in the control (e.g., confinement and guided transport) of graphene electrons, while the second provides a physical system for examining nonclassical properties of wave packets. © 2009 American Institute of Physics.
Thu, 01 Jan 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/571522009-01-01T00:00:00Z
- Robust localized modes in bilayer graphene induced by an antisymmetric kink potentialhttps://scholarbank.nus.edu.sg/handle/10635/57303Title: Robust localized modes in bilayer graphene induced by an antisymmetric kink potential
Authors: Martinez, J.C.; Jalil, M.B.A.; Tan, S.G.
Abstract: When bilayer graphene is gated with a kink potential, pair particle localization occurs at the kink where a particle (electron) and its chiral partner (hole) are held in balance by electrostatic coupling. Zero-energy states (zero modes) are always present in pairs and occur at the same point in the dispersion graph, regardless of kink strength. The robust and binary nature of the kink-induced modes, which are topologically protected against disorder, and the ease with which a kink is created suggest applications in switching devices or information storage. © 2009 American Institute of Physics.
Thu, 01 Jan 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/573032009-01-01T00:00:00Z
- Klein tunneling and zitterbewegung and the formation of a polarized p-n junction in graphenehttps://scholarbank.nus.edu.sg/handle/10635/56445Title: Klein tunneling and zitterbewegung and the formation of a polarized p-n junction in graphene
Authors: Martinez, J.C.; Jalil, M.B.A.; Tan, S.G.
Abstract: The Klein tunneling of charge pairs in an electrostatically created p-n junction of monolayer graphene is shown to occur at an observable rate for moderate fields. The pairs undergo zitterbewegung (ZBW) in opposite directions leading to their separation and transverse dipole moment, since the valleys contribute constructively. The dipole moment depends critically on the exponential collimation characteristic of Klein tunneling and serves as a diagnostic signature of ZBW. © 2010 American Institute of Physics.
Mon, 09 Aug 2010 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/564452010-08-09T00:00:00Z
- Giant Faraday and Kerr rotation with strained graphenehttps://scholarbank.nus.edu.sg/handle/10635/56139Title: Giant Faraday and Kerr rotation with strained graphene
Authors: Martinez, J.C.; Jalil, M.B.A.; Tan, S.G.
Abstract: Polarized electromagnetic waves passing through (reflected from) a dielectric medium parallel to a magnetic field undergo Faraday (Kerr) rotation of their polarization. Recently, Faraday rotation angles as much as 0.1 rad were observed for terahertz waves propagating through graphene over a SiC substrate. We show that the same effect is observable with the magnetic field replaced by an in-plane strain field which induces a pseudomagnetic field in graphene. With two such sheets a rotation of p/4 can be achieved, which is the required rotation for an optical diode. Similarly a Kerr rotation of 1/4 rad is predicted from a single reflection from a strained graphene sheet. © 2012 Optical Society of America.
Wed, 01 Aug 2012 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/561392012-08-01T00:00:00Z
- Gaussian curvature energy of graphene sheetshttps://scholarbank.nus.edu.sg/handle/10635/82402Title: Gaussian curvature energy of graphene sheets
Authors: Martinez, J.C.; Jalil, M.B.A.
Abstract: The energy density of an elastic sheet is the sum of a mean curvature H term, 2kcH2, and a Gaussian curvature K term, k̄K, where kc, k̄ are constants. The sign of kc is commonly understood to be positive, but the sign of k̄ and even the role of K are subject to debate. We give reasons for the Gaussian contribution to be k̄|K| instead, with k̄ positive. This is used to obtain the mean amplitude of thermal fluctuations of a graphene sheet. © 2011 Elsevier B.V. All rights reserved.
Mon, 13 Jun 2011 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/824022011-06-13T00:00:00Z
- Creation of "dark-soliton" atomshttps://scholarbank.nus.edu.sg/handle/10635/55468Title: Creation of "dark-soliton" atoms
Authors: Martinez, J.C.
Abstract: Dark solitons are thought to always repel so that bound states of dark solitons do not form. We show that quantum fluctuations of the background induce attractive forces between dark optical solitons. We clarify the nature of these fluctuations. Together with the repulsive potential, this attractive force creates a potential similar to that in a diatomic molecule which allows for the formation of bound pairs of dark solitons. Such pairs can be useful in the creation of notch arrays and crystal-like structures. © 2011 Europhysics Letters Association.
Sat, 01 Oct 2011 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/554682011-10-01T00:00:00Z
- Charge fractionalization in biased bilayer graphenehttps://scholarbank.nus.edu.sg/handle/10635/55286Title: Charge fractionalization in biased bilayer graphene
Authors: Martinez, J.C.; Jalil, M.B.A.; Tan, S.G.
Abstract: Fractional charge may arise when fermionic zero modes exist in a topological background field. In biased bilayer graphene (BBLG), the bias plays the role of the nontrivial background field. When semi-infinite BBLG with a zigzag edge is used, the dynamics induces an odd number of zero-energy modes, which, together with the conjugation symmetry between positive-and negative-energy states, are the requisite conditions for fractionalization. Exploiting the trigonal interaction to isolate a given zero-energy mode on the zigzag edge, we consider extended and localized modes (the latter being obtained from a localized wavepacket generated by prior irradiation of the sample with an electromagnetic vortex). The valley degeneracy is lifted by a layer asymmetry, while an edge-induced spin polarization breaks the spin degeneracy. We describe scenarios for the detection of charge- edge states. © 2012 IOP Publishing Ltd.
Wed, 22 Aug 2012 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/552862012-08-22T00:00:00Z
- Optical Faraday rotation with graphenehttps://scholarbank.nus.edu.sg/handle/10635/71270Title: Optical Faraday rotation with graphene
Authors: Martinez, J.C.; Jalil, M.B.A.; Tan, S.G.
Abstract: Plane polarized electromagnetic waves propagating through a dielectric medium parallel to a magnetic field undergo Faraday rotation (FR) of their polarization. Giant Faraday rotation by as much as 0.1 rad was recently observed for terahertz waves with graphene over a SiC substrate. We show that for the (more technologically useful) optical frequency range, the same effect may be achieved with interband transitions between Landau levels formed by application of real or pseudo-magnetic fields induced by strain. At some resonant condition, the FR angle shows a sharp transition and sign reversal, which may be used to rotate the polarizations of the sodium doublet D-lines so as to be perpendicular to each other. © 2013 AIP Publishing LLC.
Tue, 07 May 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/712702013-05-07T00:00:00Z
- Theory of giant Faraday rotation and Goos-Hänchen shift in graphenehttps://scholarbank.nus.edu.sg/handle/10635/83186Title: Theory of giant Faraday rotation and Goos-Hänchen shift in graphene
Authors: Martinez, J.C.; Jalil, M.B.A.
Abstract: We give a quantum formulation of the recently observed giant Faraday rotation (FR) in monolayer graphene (Crassee I., Nat. Phys., 7 (2011) 48) which incorporates graphene's anomalous Hall effect and the resonant interplay between Landau levels and Floquet sidebands in the limit of large Fermi energy. The same formalism is then used to discuss the Goos-Hänchen (GH) shift at the interface of two media of different permittivity, with graphene at their interface. This last feature introduces current into the electromagnetic boundary conditions. For the s-polarization case, the presence of the graphene-induced surface charge causes a much larger GH shift than without charge, and its usual monotonic behavior is altered. In the p-polarization case, surface charge and current may alter the conventional GH shift in opposite ways. We predict new phenomena such as minimum GH shift and a lateral broadening of the reflected beam, all of which should be observable with current experimental capabilities. © Europhysics Letters Association 2011.
Sat, 01 Jan 2011 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/831862011-01-01T00:00:00Z