Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session T42: Physical Properties of Topological Insulators |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Claudia Felser, Max Planck Institute Room: Mile High Ballroom 4A |
Thursday, March 6, 2014 11:15AM - 11:27AM |
T42.00001: Nonlinear optical response and Schwinger mechanism in a 3D Dirac system via gauge/gravity duality Takashi Oka, Akihiko Sonoda, Koji Hashimoto Dirac electrons realised in solid states show many exotic quantum phenomena. We study theoretically the nonlinear response of 3D Dirac materials in electro-magnetic fields such as the production of electron-hole pairs via quantum tunneling, i.e., Schwinger mechanism ($=$Zener breakdown), and birefringence. This is done by calculating the Euler-Heisenberg Lagrangian, which is the generating function of nonlinear optical response coefficients ([1] is a review). We also study the effect of correlation with a QCD-like toy model using gauge-gravity duality [2] and find universal relations that are accessible with solid state experiments. [1] T. Oka, and H. Aoki, ?Nonequilibrium Quantum Breakdown in a Strongly Correlated Electron System?, LNP Springer (2008). [2] K. Hashimoto, T. Oka, JHEP 10, 116 (2013). [Preview Abstract] |
Thursday, March 6, 2014 11:27AM - 11:39AM |
T42.00002: Non-Local Quantum Transport Theory of Proximity Coupled Topological Systems Brian Dellabetta, Martin Stehno, Dale Van Harlingen, Matthew Gilbert Previous work on the coupling of s-wave superconductors (SC) and time-reversal invariant topological insulators (TIs) has revealed that the broken spin-rotation symmetry inherent in the TI surface states results in a proximity-induced order that deviates from the conventional character of the parent SC.\footnote{A. M. Black-Schaffer et al., \emph{PRB} {\bf 87}, 220506 (2013).} Despite the plethora of interesting phenomena predicted to occur in this system, knowledge about the transport manifestations of this unusual SC order have yet to be studied. In this talk, we consider an SC-TI heterostructure and determine the quantum transport signatures of this unconventional superconductivity that emerges within the mean-field picture. By combining quantum transport experiments and non-equilibrium quantum transport theory, we discuss the unique signatures which appear in the non-local differential conductance due to the unconventional superconducting state present in our SC-TI coupled system. [Preview Abstract] |
Thursday, March 6, 2014 11:39AM - 11:51AM |
T42.00003: A 3D topological insulator quantum dot for optically controlled quantum memory and quantum computing Hari Paudel, Michael Leuenberger We present the model of a quantum dot (QD) consisting of a spherical core-bulk heterostructure made of 3D topological insulator (TI) materials with bound massless and helical Weyl states existing at the interface. The number of bound states can be controlled by tuning the size of the QD and the magnitude of the core and bulk energy gaps in QD sizes of few nanometers. The confined massless Weyl states in 3D TI QDs are localized at the interface of the QD and exhibit a mirror symmetry in the energy spectrum. The strict optical selection rules give rise to the Faraday effect due to Pauli exclusion principle. We show that the semi-classical Faraday effect can be used to read out spin quantum memory. When a 3D TI QD is embedded inside a cavity, the single-photon Faraday rotation provides the possibility to implement optically mediated quantum teleportation and quantum information processing with 3D TI QDs. Remarkably, the combination of inter- and intraband transition gives rise to a large dipole moment of up to 450 Debye. The strong-coupling regime can be reached for a cavity quality factor of $Q \approx 10^4$ in the infrared wavelength regime. [Preview Abstract] |
Thursday, March 6, 2014 11:51AM - 12:03PM |
T42.00004: Modelling of the transport properties of topologically protected edge states Xiaoqian Dang, J.D. Burton, Evgeny Tsymbal One of the great successes of modern condensed matter physics is the discovery of topological insulators (TI). A thorough investigation of their transport properties, along with proposed device geometries, could bring such materials from fundamental research to potential applications. Here we report on theoretical investigations of transport properties of simple systems which incorporate TIs and their protected edge states. We utilize the tight-binding form of the Bernevig-Hughes-Zhang model [1] as a prototype for generic topological insulators. Transport properties are investigated theoretically by constructing the Green's functions and employing the Landauer-B\"{u}ttiker formalism. We study the limitations to scattering-free transport around defects/impurities through topologically protected edge states, as well as the prospect of metal-TI-metal tunnel junctions where the protected edge states reside between the metal electrode and the insulating bulk of the TI. Elucidating the fundamental physical effects that occur in these (and other) systems will be an integral step in establishing TIs as a building block for potential electronic device applications.\\[4pt] [1] B. A. Bernevig \textit{et al}., \textit{Science}, \textbf{314}, 1757 (2006). [Preview Abstract] |
Thursday, March 6, 2014 12:03PM - 12:15PM |
T42.00005: Anisotropic Quantum Spin Hall Effect, Spin-Orbital Textures and Mott Transition Tianhan Liu, Benoit Doucot, Karyn Le Hur We investigate the interplay between topological effects and Mott physics in 2D on a graphene-like lattice, via a tight-binding model containing an anisotropic spin-orbit coupling on the next-nearest-neighbour links and the Hubbard interaction. We thoroughly analyze the resulting phases, namely an anisotropic quantum Spin Hall phase until moderate interactions, a Neel and Spiral phase at large interactions in the Mott regime, as well as the formation of a spin-orbital texture in the bulk at the Mott transition. At weak interactions, the system is described through a $Z_2$ topological invariant and we describe how the anisotropic spin-orbit coupling already produces an exotic spin texture at the edges. The physics at the Mott transition is described in terms of a U(1) slave rotor theory. Taking into account gauge fluctuations around the mean-field saddle point solution, we show how the spin texture now proliferates into the bulk above the Mott critical point. The latter emerges from the response of the spinons under the insertion of monopoles and this becomes more pronounced as the spin-orbit coupling becomes prevalent. We discuss implications of our predictions for thin films of the iridate compound Na$_2$IrO$_3$ and also graphene-like systems. [Preview Abstract] |
Thursday, March 6, 2014 12:15PM - 12:27PM |
T42.00006: Giant magnetoresistance in the junction of two ferromagnets on the surface of diffusive topological insulators Katsuhisa Taguchi, Takehito Yokoyama, Yukio Tanaka We reveal the giant magnetoresistance induced by the spin-polarized current in the ferromagnet (F$_1$)/topological insulator (TI)/ferromagnet (F$_2$) junction, where two ferromagnets are deposited on the diffusive surface of the TI. We can increase and reduce the value of the giant magnetoresistance by tuning the spin-polarized current, which is controlled by the magnetization configurations. The property is intuitively understood by the non-equilibrium spin-polarized current, which plays the role of an effective electrochemical potential on the surface of the TI. [Preview Abstract] |
Thursday, March 6, 2014 12:27PM - 12:39PM |
T42.00007: ABSTRACT WITHDRAWN |
Thursday, March 6, 2014 12:39PM - 12:51PM |
T42.00008: Transport discovery of emerged robust helical surface states in $Z_2=0$ systems Hua Jiang, Haiwen Liu, Ji Feng, Qingfeng Sun, X.C. Xie We study the possibility of realizing robust helical surface states in $Z_2=0$ systems. We find the emergence of robust helical edge (surface) states in both 2D and 3D $Z_2=0$ systems, arising from anisotropic confinement in a finite-size sample. Based on transport simulations of anisotropic Bernevig-Hughes-Zhang (BHZ) model, we demonstrate quantized conductance of helical edge states under strong nonmagnetic disorders. The robustness of helical surface states due to anisotropic confinement is generalizable to 3D weak topological insulators. Moreover, the proposed $Z_2=0$ systems possess additional exotic properties than in $Z_2=1$ TIs. In particular, by controlling the sample size and strain engineered anisotropy, this mechanism allows for efficient tuning of the effective energy gap, and fabrication of valley filter and valley valve without breaking time reversal symmetry. [Preview Abstract] |
Thursday, March 6, 2014 12:51PM - 1:03PM |
T42.00009: Diode-Free Photocurrents in Solid State Dirac Systems Netanel Lindner, Gil Refael, Felix von Oppen Producing photocurrents on surfaces of topological insulators has tremendous potential for infrared photo-energy harvesting and detection. Unfortunately, careful analysis of photocurrent generation in topological insulators showed that any effect is minuscule. Here we demonstrate that a significant photocurrent can be generated in a topological insulator surface, and other two dimensional electronic gases with Dirac dispersion, when a spatially periodic magnetic texture is coupled to the surface. We show that this can be achieved by patterning the surface with strips of magnetic material. Applications of devices obtained using the proposed method range from photovoltaic harvesting of infra-red solar energy to low frequency GHZ-THZ photon detectors. [Preview Abstract] |
Thursday, March 6, 2014 1:03PM - 1:15PM |
T42.00010: Proximity effect in graphene-topological insulator heterostructures E. Rossi, Junhua Zhang, Christopher Triola We study the effect on graphene and bilayer graphene of the proximity of a strong three dimensional (3D) topological insulator (TI) by considering heterostructures formed by one sheet of graphene, or bilayer graphene, stacked on a strong 3D TI. We consider both the case of commensurate and incommensurate stacking. Our results [1] show that the proximity of the TI strongly enhances the spin-orbit coupling in the graphenic layer, especially for the case of bilayer graphene. We also find that, both for the commensurate and the incommensurate case, the hybridization of the graphene and TI states gives rise to bands with non-trivial spin and pseudospin textures.\\[4pt] [1] Junhua Zhang, C. Triola, E, Rossi, arXiv:1308.6287. [Preview Abstract] |
Thursday, March 6, 2014 1:15PM - 1:27PM |
T42.00011: Numerical study of Fibonacci anyons in superconductor/quantum Hall structures Edwin Miles Stoudenmire, David Clarke, Roger Mong, Jason Alicea We apply the density matrix renormalization group (DMRG) to ladders of coupled Z3 parafermions (a type of abelian anyon) following the proposal of Mong, Clarke, et al. who showed that such parafermions can in principle be engineered in superconductor/quantum Hall heterostructures and then coupled to form a gapped 2d phase supporting non-abelian Fibonacci anyons. Because DMRG works well for gapped phases and can handle arbitrarily strong interactions, it complements Mong et al.'s analytical approach based on weakly coupled critical chains. We establish the basic phase diagram and verify key properties of the 2d Fibonacci phase. [Preview Abstract] |
Thursday, March 6, 2014 1:27PM - 1:39PM |
T42.00012: Two-particle and single-particle spin-dependent interactions in topological insulators Marius Radu, Yuli Lyanda-Geller We derive single-particle and two-particle interaction Hamiltonians describing physics of two-dimensional topological insulators based on HgTe-CdTe quantum well structures by using $\mathbf{k}\cdot\mathbf{p}$ theory and extended Kane model. We include contributions from upper conduction band with orbital states of p-symmetry that bring about the terms describing lack of inversion symmetry in host semiconductors. Single-particle Hamiltonian and two-particle Hamiltonian contain important spin-dependent diagonal and off-diagonal terms. We demonstrate how these terms affect spin currents, interference effects in conductance such as weak localization and anti-localization, and contribute to spin relaxation and dephasing. The spin-dependent interaction terms couple orbital motion of one particle with evolution of spin of the other particle. Such particle-particle interactions do not conserve spin and lower the symmetry of exchange interactions, leading, e.g., to Dzyaloshinskii-Moriya exchange term. [Preview Abstract] |
Thursday, March 6, 2014 1:39PM - 1:51PM |
T42.00013: Study of correlated topological insulators in one dimension Tsuneya Yoshida, Robert Peters, Satoshi Fujimoto, Norio Kawakami In correlated topological insulators, various exotic phenomena are expected. For instance, realization of an exotic Mott insulator where one can observe gapless edge modes in the spinon excitation instead of the single particle excitation is proposed. Unfortunately, however, this exotic behavior has not been well established so far. In this article, we explore possibilities of this behavior and find the aforementioned edge behavior in one dimensional systems, which can be understood with symmetry reduction under the Shiba transformation. Furthermore, we also propose a topological Mott transition which is a new type of topological phase transition and never observed in free fermion systems. This unconventional transition occurs in spin liquid phases and is accompanied by zeros of the single particle Green's function and gap closing in the spin excitation spectrum. [Preview Abstract] |
Thursday, March 6, 2014 1:51PM - 2:03PM |
T42.00014: Quasiparticle electronic structure of bulk and slab Bi$_{2}$Se$_{3}$ and Bi$_{2}$Te$_{3}$ Bradford Barker, Jack Deslippe, Oleg Yazyev, Steven G. Louie We present ab initio calculations of the quasiparticle electronic band structure of three-dimensional topological insulator materials Bi$_{2}$Se$_{3}$ and Bi$_{2}$Te$_{3}$. The mean-field DFT calculation is performed with fully relativistic pseudopotentials, generating spinor wavefunctions in a plane-wave basis. Quasiparticle properties are computed with a one-shot ab initio GW calculation. We use both bulk and slab forms of the materials to better understand the quasiparticle band gaps and Fermi velocities of the topological surface states of these materials. [Preview Abstract] |
Thursday, March 6, 2014 2:03PM - 2:15PM |
T42.00015: Theory of quantum Hall nematic phases Yizhi You, Gil Young Cho, Eduardo Fradkin Motivated by the experiments by Xia et al, we derive and study the effective field theories of isotropic-nematic quantum phase transitions of Chern insulators and FQH states. In both cases, we demonstrate that the low-energy theory of nematic order parameter has z=2 dynamics due to a Berry phase term of the nematic order, which is related with the Hall viscosity in parity and TRS broken states. We present a composite fermion theory for a FQH fluid with attractive quadrupolar interactions which, if strong enough, trigger a transition to a nematic phase. By investigating the excitation spectrum at RPA level, we demonstrate that at the quantum phase transition the energy gap of Girvin-MacDonald-Plazman mode condenses at zero momentum. The topological nature of the fluid is not affected by the transition, the Laughlin quasiparticles remain gapped, the Kohn mode gap is unaffected, and Kohn's theorem is satisfied. In the nematic phase, the nematic order parameter can be regarded as a deformation of the local geometry and couples as a metric to the Maxwell terms of the gauge fields. The vortex of the nematic field, a disinclination, will also be mentioned. We discuss the relation of our results with those of Mulligan et al, and Maciejko et al. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700