Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session X12: Topological Materials: Theory and Experiment |
Hide Abstracts |
Sponsoring Units: DCMP DMP Room: 308 |
Friday, March 18, 2016 8:00AM - 8:12AM |
X12.00001: Phase diagram of disordered, time reversal invariant topological superconductors in two and three dimensions Sudip Chakravarty, Pallab Goswami In the absence of spin rotational invariance, time reversal symmetric topological superconducting states (belonging to the class DIII) can be realized in all three spatial dimensions. We construct the global phase diagrams of disordered, class DIII superconductors in two and three dimensions. In both spatial dimensions the Bogoliubov de Gennes quasiparticles can exhibit two topologically distinct localized (gapped) phases, in addition to a diffusive (gapless) phase that possesses metallic thermal conductivity. We also obtain exact localization length exponents and approximate crossover scaling functions for the relevant topological quantum phase transitions. For sufficiently weak disorder, we show that the direct topological transition between two gapped states is described by a four component, massless Dirac fermion with a dynamical exponent $z=1$ and a correlation/localization length exponent $\nu_M=1$. For stronger disorder, we demonstrate how two topologically distinct localized states and the delocalized diffusive phase meet at a line of disorder controlled fixed points, which governs the nature of the localization-delocalization transitions. We show the existence of a universal localization length exponent $\nu_M=2/d$ and a nonuniversal dynamical exponent for the localizati [Preview Abstract] |
Friday, March 18, 2016 8:12AM - 8:24AM |
X12.00002: Converting a topologically trivial superconductor into a chiral topological superconductor via diluted magnetic doping Wei Qin, Di Xiao, Kai Chang, Shun-Qing Shen, Zhenyu Zhang We employ two complementary theoretical approaches to explore the feasibility of altering the topological properties of two-dimensional Rashba spin-orbit coupled superconductors by proper introduction of magnetic disorders. First, using the self-consistent Born approximation, we show that a topologically trivial superconductor can be driven into a chiral topological superconductor upon diluted doping of isolated magnetic disorders, which gradually narrow, close, and reopen the quasi-particle gap of the paired electrons in a nontrivial manner. Such a topological phase transition is further characterized by the change in the corresponding topological invariant. The central predictions made here are then confirmed using the complementary numerical approach by solving the Bogoliubov-de Gennes equations self-consistently within a tight-binding model. We also discuss the validity of the present model studies in connection with existing experimental findings. Collectively, the present study offers appealing new schemes for potential experimental realization of topological superconductors. [Preview Abstract] |
Friday, March 18, 2016 8:24AM - 8:36AM |
X12.00003: Quantum Monte Carlo study of strange correlator in interacting topological insulators Han-Qing Wu, Yuan-Yao He, Yi-Zhuang You, Cenke Xu, Zi Yang Meng, Zhong-Yi Lu Distinguishing the nontrivial symmetry-protected topological (SPT) phase from the trivial insulator phase in the presence of electron-electron interaction is an urgent question to the study of topological insulators. In this work, we demonstrate that the strange correlator is a sensitive diagnosis to detect SPT states in interacting systems. Employing large-scale quantum Monte Carlo (QMC) simulations, we investigate the interaction-driven quantum phase transition in the Kane-Mele-Hubbard model. The transition from the quantum spin Hall insulator at weak interaction to an antiferromagnetic Mott insulator at strong interaction can be readily detected by the momentum space behavior of the strange correlator in single-particle, spin, and pairing sectors. The interaction e?ects on the symmetry-protected edge states in various sectors are well captured in the QMC measurements of strange correlators. Moreover, we demonstrate that the strange correlator is technically easier to implement in QMC and more robust in performance than other proposed numerical diagnoses for interacting topological states, as only static correlations are needed. The attempt in this work paves the way for using the strange correlator to study interaction-driven topological phase transitions. [Preview Abstract] |
Friday, March 18, 2016 8:36AM - 8:48AM |
X12.00004: Avoided quantum criticality in disordered three-dimensional Dirac semi-metals Jedediah Pixley, David Huse We study the effects of short-range random potential disorder on three-dimensional Dirac semi-metals. We focus on the proposed quantum critical point (QCP) separating a semi-metal and diffusive metal phase driven by disorder. We will briefly review the existing evidence of such a QCP. We will then explore the non-perturbative effects of rare regions using Lanczos and the kernel polynomial method, from which we establish the existence of two distinct types of excitations in the weak disorder regime. The first are perturbatively renormalized dispersive Dirac states and the second are weakly dispersive quasi-localized ``rare'' eigenstates. We establish that these rare eigenstates contribute an exponentially small but non-zero density of states at zero energy, thus converting the semi-metal to diffusive metal transition into an avoided quantum critical point. [Preview Abstract] |
Friday, March 18, 2016 8:48AM - 9:00AM |
X12.00005: Explicit derivation of duality between a free Dirac cone and quantum electrodynamics in (2+1) dimensions David F. Mross, Jason Alicea, Olexei I. Motrunich A single Dirac cone of (free) electrons famously arises on the surface of a 3D topological insulator. Recent work proposed that these metallic surfaces can alternatively be described by quantum electrodynamics in $(2+1)$ dimensions (QED$_3$), where charge-neutral 'dual fermions' strongly couple to an emergent photon. We explicitly derive this duality via an exact, non-local mapping from electrons to dual fermions on the level of path integrals. This mapping allows us to construct Hamiltonians for exotic topological-insulator surface phases, and to derive the particle-hole-symmetric field theory of a half-filled Landau level. By running the duality 'in reverse' we can constrain scaling dimensions for operators in QED$_3$ and establish duality between bosonic topological insulator surfaces and QED$_3$ with two fermion flavors. [Preview Abstract] |
Friday, March 18, 2016 9:00AM - 9:12AM |
X12.00006: Correlation effects in 3D triple-Weyl semimetals Shi-Xin Zhang, Shao-Kai Jian, Hong Yao We study interaction effects, including short-range interactions and long-range Coulomb interactions, in three-dimensional topological triple-Weyl semimetals whose triple-Weyl points are protected by crystalline symmetries. In the low-energy effective field theory of triple-Weyl semimetals, by considering symmetries and utilizing Fierz identity, we find that there are only four independent short-range interaction terms. We then perform Wilsonian renormalization group analysis to determine the effect of short-range interactions at low energy and long distance by finding fixed points as well as stable strong-coupling limits. For those strong-coupling limits due to short-range interactions, spontaneous symmetry-breaking ordering is expected and is analyzed by self-consistent mean-field calculations combined with RG flow. For long-range Coulomb interactions, we find anisotropic screening effect, similar with the one in double-Weyl semimetals, and hence a qualitatively different fixed point from the Gaussian one. [Preview Abstract] |
Friday, March 18, 2016 9:12AM - 9:24AM |
X12.00007: First-Principles Design of a Half-Filled Flat Band of the Kagome Lattice in Two-Dimensional Metal-Organic Frameworks Masahiko G. Yamada, Tomohiro Soejima, Naoto Tsuji, Daisuke Hirai, Mircea Dinc\u{a}, Hideo Aoki Metal-organic frameworks (MOFs) are crystalline materials composed of metal ions and bridging organic molecules, which have been the subject of numerous investigations in inorganic and materials chemistry. Owing to their typically trivial electronic states, MOFs have not attracted much attentions from condensed-matter physicists. However, recent experimental success in fabricating two-dimensional (2D) MOFs with kagome lattice structures is bridging the gap between condensed-matter physics and chemistry. Then, we design from first principles a new type of 2D MOFs with phenalenyl-based ligands to realize a half-filled flat band of the kagome lattice, which belongs to the lattice family that shows Lieb-Mielke-Tasaki's flat-band ferromagnetism. We find that \textit{trans}-Au-THTAP(trihydroxytriaminophenalenyl) has an ideal band structure, where the Fermi energy is adjusted right at the nearly flat band. The spin-orbit coupling opens a band gap and gives a non-zero Chern number to the nearly flat band. This is a novel and realistic example of a system in which a nearly flat band is both ferromagnetic and topologically non-trivial. See arXiv:1510.00164. [Preview Abstract] |
Friday, March 18, 2016 9:24AM - 9:36AM |
X12.00008: Nernst and magneto-thermal conductivity in a lattice model of Weyl fermions Girish Sharma, Pallab Goswami, Sumanta Tewari Weyl semimetals (WSM) are topologically protected three dimensional materials whose low energy excitations are linearly dispersing massless Dirac fermions, possessing a non-trivial Berry curvature. Using semi-classical Boltzmann dynamics in the relaxation time approximation for a lattice model of time reversal (TR) symmetry broken WSM, we compute both magnetic field dependent and anomalous contributions to the Nernst coefficient. In addition to the magnetic field dependent Nernst response, which is present in both Dirac and Weyl semimetals, we show that, contrary to previous reports, the TR-broken WSM also has an anomalous Nernst response due to a non-vanishing Berry curvature. We also compute the thermal conductivities of a WSM in the Nernst (${\nabla T} \perp \mathbf{B}$) and the longitudinal (${\nabla T} \parallel \mathbf{B}$) set-up and confirm from our lattice model that in the parallel set-up, the Wiedemann-Franz law is violated between the longitudinal thermal and electrical conductivities due to chiral anomaly. [Preview Abstract] |
Friday, March 18, 2016 9:36AM - 9:48AM |
X12.00009: Topological edge states in pnictides Cody Youmans, Pouyan Ghaemi, Mehdi Kargarian In some members of the ferro-pnictides, non-trivial topology in the bulk band-structure is related to potentially observable gapless edge states. We study these states numerically and analytically for a range of parameters, with and without superconductivity and antiferromagnetic SDW ordering, and their relation to the symmetries and topologically non-trivial aspects of our model Hamiltonian. [Preview Abstract] |
Friday, March 18, 2016 9:48AM - 10:00AM |
X12.00010: Symmetry-enriched topological invariants from tensor network representations Brayden Ware, Meng Cheng, Bela Bauer We examine topologically ordered quantum phases in 2+1 dimensions where in the presence of symmetries the topological phase splits into multiple symmetry enriched topological (SET) phases. These SET phases become adiabatically connected when the symmetry is broken, but are separated by phase transitions when symmetry is enforced. Using tensor network representations of representative wavefunctions for certain SET phases, we demonstrate the calculation of the extended modular matrices, a generalization of the well-known modular matrices that have been used to robustly characterize topological phases in numerical calculations. Here, the crucial extension is to systems with symmetry defects. The extended modular matrices are used to form symmetry-enriched topological invariants which distinguish different SET phases. [Preview Abstract] |
Friday, March 18, 2016 10:00AM - 10:12AM |
X12.00011: Electronic structure studies of topological materials Shuyun Zhou Three-dimensional (3D) Dirac fermions are a new class of topological quantum materials. In 3D Dirac semimetals, the conduction and valence bands touch each other at discrete points in the momentum space and show linear dispersions along all momentum directions, forming 3D Dirac cones which are protected by the crystal symmetry. Here I will present our recent studies of the electronic structures of novel materials which host 3D Dirac fermions by using angle-resolved photoemission spectroscopy. [Preview Abstract] |
Friday, March 18, 2016 10:12AM - 10:24AM |
X12.00012: Propagation of Surface Plasmon Polaritons in Thin Films of Topological Insulators Yury Deshko, Zhiyi Chen, Lia Krusin-Elbaum, Vinod Menon, Jacob Trevino, Alexander Khanikaev Surface Plasmon Polaritons (SPP) are coupled collective oscillations of surface charges and electromagnetic waves confined to the interface between a metal and a dielectric. Three dimensional topological insulators (TI), such as Bi$_2$Se$_3$, Bi$_2$Te$_3$, and Sb$_2$Te$_3$ are narrow band-gap semiconductors in the bulk while having conducting surface with the linear energy dispersion for the surface electronics states. Similar to double-layered graphene a thin single film of TI supports two SPP modes in the far-infrared range. We study the propagation of these modes in thin films of Bi$_2$Se$_3$, Bi$_2$Te$_3$, and Sb$_2$Te$_3$. The dispersion curves and the propagation lengths are estimated for all three materials. The explanation of the discrepancy between the theory [1] and the first experimental observation of standing wave SPPs in Bi$_2$Se$_3$ [2] is proposed. Finally, the possibilities of tuning the SPP dispersion relations in thin films of TI are discussed.\\ $\lbrack 1\rbrack$ T. Stauber, G. Gomez-Santos, and L. Brey, Phys. Rev. B 88, 205427 (2013).\\ $\lbrack 2\rbrack$ P. Di Pietro, M. Ortolani, O. Limaj, A. Di Gaspare, V. Giliberti, F.\\ Giorgianni, M. Brahlek, N. Bansal, N. Koirala, S. Oh, P. Calvani, and S. Lupi, Nature Nanotechnology 8, 556 (2013). [Preview Abstract] |
Friday, March 18, 2016 10:24AM - 10:36AM |
X12.00013: Observation of a topologically non-trivial surface state in half-Heusler PtLuSb (001) thin films John Logan, Sahil Patel, Sean Harrington, Craig Polley, Brian Schultz, T. Balasubramanian, Anderson Janotti, Anders Mikkelsen, Chris Palmstrøm Topological insulators are a recently discovered new quantum state of matter that has a bulk band gap but also possesses cross-gap surface states which are protected by time-reversal symmetry. The experimental realization of topologically non-trivial surface states (TSSs) in materials such as Bi$_{\mathrm{2}}$Se$_{\mathrm{3}}$ has generated widespread interest in identifying other material systems that exhibit TSSs due to their many uses including spintronic devices. In particular, recent theory calculations suggest that TSSs may be found in certain half-Heusler ternary compounds. If experimentally realizable, this would provide an opportunity for the creation of entirely new heterostructure spintronic devices that make use of the structurally-identical but electronically-varied nature of Heusler compounds. Here, we show the presence of a TSS in the half-Heusler compound PtLuSb. Spin and angle-resolved photoemission spectroscopy reveals a surface state with linear dispersion and a helical tangential spin texture consistent with theoretical predictions and the expectation for a topological insulator. [Preview Abstract] |
Friday, March 18, 2016 10:36AM - 10:48AM |
X12.00014: Predicted Growth of Two-Dimensional Topological Insulators Consisting of Hydrogenated III-V Thin films on Si(111) Substrate Feng-Chuan Chuang, Christian Crisostomo, Liang-Zi Yao, Chun-Chen Yeh, Shu-Ming Lai, Zhi-Quan Huang, Chia-Hsiu Hsu, Hsin Lin, Marvin Albao, Arun Bansil We have carried out systematic first-principles electronic structure calculations of growth of ultrathin films of compounds of group III (B, Al, In, Ga and Tl) with group V (N, P, As, Sb and Bi) elements on Si(111) substrate, including effects of hydrogenation. A total of six compounds (GaBi, InBi, TlBi, TlAs, TlSb and TlN) are identified to be nontrivial in unhydrogenated case; whereas for hydrogenated case, only four (GaBi, InBi, TlBi and TlSb) remains nontrivial. The band gap is found to be as large as 855 meV for the hydrogenated TlBi film, making this class of III-V materials suitable for room temperature applications. TlBi remains topologically nontrivial with a large band gap at various hydrogen coverages, indicating the robustness of its band topology against bonding effects of substrates. Two bilayers (BLs) of AlBi, InBi, GaBi, TlAs and TlSb are found to support a topological phase over a wide range of strains, in addition to BBi, TlN and TlBi which can be driven into the nontrivial phase via strain. One and two BL films of GaBi and 2 BL films of InBi and TlAs on Si(111) surface possess nontrivial phases with a band gap as large as 121 meV in the case of 2 BL film of GaBi. Persistence of the nontrivial phase upon hydrogenations in the III-V thin films suggests that these films are suitable for growing on various substrates. [Preview Abstract] |
Friday, March 18, 2016 10:48AM - 11:00AM |
X12.00015: Transport properties of superconducting high indium-doped SnTe single crystals Cheng Zhang, Ruidan Zhong, Genda Gu, Qiang Li The discovery of topological crystalline insulator SnTe has ignited a search for the predicted topological superconductors. Recently, we performed the transport measurement on a series of indium-doped SnTe single crystals (Sn$_{\mathrm{1-x}}$In$_{\mathrm{x}}$Te). Hall measurement shows that carrier type changes when indium doping level is between x $=$ 0.2 and 0.3. Weak anti-localization effect and Shubnikov-de Hass oscillations was found in x $=$ 0.45 samples, which have the highest superconducting transition temperature at 4.5 K. Both superconducting and normal state properties of high indium-doped SnTe will be discussed. [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