Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session W34: Topological Systems and Quantum Dynamics |
Hide Abstracts |
Sponsoring Units: DAMOP Chair: Alexey Gorshkov, Joint Quantum Institute Room: 704 |
Thursday, March 6, 2014 2:30PM - 2:42PM |
W34.00001: Spin supercurrents and torquing with Majorana fermions Kirill Shtengel, Alexey Kovalev, Amrit De We show that resonant coupling and entanglement between a mechanical resonator and majorana bound states can be achieved via spin supercurrents in a 1D quantum wire with strong spin-orbit interactions in the proximity of s-wave superconductor. The bound states induced by vibrating and stationary magnets can hybridize thus resulting in spin-current induced {\$}4$\backslash $pi{\$}-periodic torque, as a function of the relative field angle, acting on the resonator. We propose a realization based on spin transistor like architecture in which a heterostructure nanowire consists of semiconductors with large and small g-factors in order to form the topological and non-topological regions. We also study the feasibility of detecting and manipulating majorana bound states with the use of magnetic resonance force microscopy techniques. [Preview Abstract] |
Thursday, March 6, 2014 2:42PM - 2:54PM |
W34.00002: Floquet generation of Majorana edge modes and topological invariants Diptiman Sen, Manisha Thakurathi, Aavishkar Patel, Amit Dutta, Krishnendu Sengupta We show that periodic driving of one of the parameters in the Hamiltonian of a system can produce Majorana modes at its edges. The systems studied include a $p$-wave superconducting wire and the Kitaev model on the honeycomb lattice. For the wire, we show that periodic $\delta$-function kicks of the on-site potential can produce a number of Majorana modes at the two ends; these modes can appear or disappear as the driving frequency is varied. The end modes correspond to eigenvalues of the Floquet operator equal to $\pm 1$. Using Floquet theory for the bulk, we derive a topological invariant which correctly predicts the number of these modes as a function of the frequency and the Floquet eigenvalue. We also discuss the generation of end modes by periodic kicking of the hopping and superconducting terms. For the Kitaev model, we derive the phase diagram where Majorana edge modes appear on zigzag and armchair edges. We then show that if one of the couplings is given periodic $\delta$-function kicks, modes can appear on some edges even when the corresponding equilibrium Hamiltonian has no modes on those edges. The Floquet theory of the bulk can again be used to predict the frequencies at which edge modes appear or disappear for different values of the momentum of the modes. [Preview Abstract] |
Thursday, March 6, 2014 2:54PM - 3:06PM |
W34.00003: Quantum Quenches in Topological Systems Graham Kells, Diptiman Sen, J.K. Slingerland, Smitha Vishveshwara We study the non-equilibrium dynamics of quenching through a quantum critical point in topological systems, focusing on one of their characteristic features, namely, ground state degeneracies, and associated topological sectors. We present the notion of ``topological blocking,'' experienced by the dynamics due to the mismatch in degeneracies between two phases. We demonstrate the interplay between quenching and topology in two extensively studied systems, the transverse Ising chain and the Kitaev honeycomb model. Casting these systems in the language of fermionic spinless p-wave paired superconductors enables us to cleanly address degeneracies, subtle issues of fermion occupation and parity, and mismatches between topological sectors. We show that several features of the quench, which are related to Kibble-Zurek physics, are sensitive to the topological sector being probed. [Preview Abstract] |
Thursday, March 6, 2014 3:06PM - 3:18PM |
W34.00004: Hidden-Symmetry-Protected Topological Semimetals on a Square Lattice Jing-Min Hou We study a two-dimensional fermionic square lattice, which supports the existence of two-dimensional Weyl semimetal, quantum anomalous Hall effect, and $2\pi$-flux topological semimetal in different parameter ranges. We show that the band degenerate points of the two-dimensional Weyl semimetal and $2\pi$-flux topological semimetal are protected by two distinct novel hidden symmetries, which both corresponds to antiunitary composite operations. When these hidden symmetries are broken, a gap opens between the conduction and valence bands, turning the system into a insulator. With appropriate parameters, a quantum anomalous Hall effect emerges. The degenerate point at the boundary between the quantum anomalous Hall insulator and trivial band insulator is also protected by the hidden symmetry. [PRL 111, 130403(2013)] [Preview Abstract] |
Thursday, March 6, 2014 3:18PM - 3:30PM |
W34.00005: Topological superfluids with finite-momentum pairing and Majorana fermions Chunlei Qu, Zhen Zheng, Ming Gong, Yong Xu, Li Mao, Xubo Zou, Guangcan Guo, Chuanwei Zhang Majorana fermions (MFs), quantum particles that are their own antiparticles, are not only of fundamental importance in elementary particle physics and dark matter, but also building blocks for fault-tolerant quantum computation. Recently MFs have been intensively studied in solid state and cold atomic systems. These studies are generally based on superconducting pairing with zero total momentum. On the other hand, finite total momentum Cooper pairings, known as Fulde-Ferrell (FF) Larkin-Ovchinnikov (LO) states, were widely studied in many branches of physics. However, whether FF and LO superconductors can support MFs has not been explored. Here we show that MFs can exist in certain types of gapped FF states, yielding a new quantum matter: topological FF superfluids/superconductors. We demonstrate the existence of such topological FF superfluids and the associated MFs using spin-orbit-coupled degenerate Fermi gases and derive their parameter regions. The implementation of topological FF superconductors in semiconductor/superconductor heterostructures is also discussed. [Preview Abstract] |
Thursday, March 6, 2014 3:30PM - 3:42PM |
W34.00006: Singlet Mott State Simulating the Bosonic Laughlin Wave Function Biao Lian, Shou-Cheng Zhang We study properties of a class of spin singlet Mott states for arbitrary spin $S$ bosons on a lattice, with particle number per cite $n=S/l+1$, where $l$ is a positive integer. We show that such a singlet Mott state can be mapped to a bosonic Laughlin wave function on the sphere with a finite number of particles at filling $\nu=1/2l$. Bosonic spinons, particle and hole excitations in the Mott state are discussed, among which the hole excitation can be mapped to the quasi-hole of the bosonic Laughlin wave function. We show that this singlet Mott state can be realized in a cold atom system on optical lattice, and can be identified using Bragg spectroscopy and Stern-Gerlach techniques. This class of singlet Mott states may be generalized to simulate bosonic Laughlin states with filling $\nu=q/2l$. [Preview Abstract] |
Thursday, March 6, 2014 3:42PM - 3:54PM |
W34.00007: Realizing topological states with polyatomic symmetric top molecules Michael Wall, Kenji Maeda, Lincoln Carr We show how to use polyatomic symmetric top molecules, such as methyl fluoride, in an optical lattice to produce states with non-trivial topology via a self-consistent analog of the proximity effect in the internal state space of the molecule. The key ingredient is pairwise transitions between internal states of a molecule which are generated by the dipole-dipole interaction and made resonant by a combination of static and AC electric field dressing. These pairwise transitions endow the effective many-body Hamiltonian with a U(1)$\times$Z$_2$ symmetry leading to topologically nontrivial states. We will present results of matrix product state simulations demonstrating non-trivial topology, and also provide mappings of the many-body description to models of quantum spins with un-conserved magnetization as well as to systems with Majorana fermion excitations. [Preview Abstract] |
Thursday, March 6, 2014 3:54PM - 4:06PM |
W34.00008: Topological Bose-Mott Insulators in a One-Dimensional Optical Superlattice Shi-Liang Zhu, Z.D. Wang, Y.H. Chan, L.M. Duan In this talk, I will introduce topological Bose-Mott insulators we found in a one-dimensional optical superlattice. We study topological properties of the Bose-Hubbard model with repulsive interactions in a one-dimensional optical superlattice, and find that the Mott insulator states of the single-component (two-component) Bose-Hubbard model under fractional fillings are topological insulators characterized by a nonzero charge (or spin) Chern number with nontrivial edge states. For ultracold atomic experiments, we show that the topological Chern number can be detected through measuring the density profiles of the bosonic atoms in a harmonic trap. Ref.: S.L. Zhu, Z.D. Wang, Y.H. Chan, and L.M. Duan, Phys. Rev. Lett. 110, 075303 (2013). [Preview Abstract] |
Thursday, March 6, 2014 4:06PM - 4:18PM |
W34.00009: Detection of topological excitations in atom circuits via phase reference C. Lanier, N. Murray, M. Edwards, C.W. Clark Atom circuits (such as ring Bose--Einstein condensates [BECs]) can now be implemented in ultracold--atom systems confined in a horizontal plane with a red--detuned light sheet plus an essentially arbitrary two--dimensional potential in the plane. Atom--circuit operation may be effected by subsequent interaction with the system (such as stirring a ring BEC with a blue--detuned laser). These interactions will create topological excitations such as solitons and ring-- and line--vortices which may be critical to circuit operation. It is therefore interesting to study methods by which such topological excitations can be detected and to identify the various signatures whereby the different excitations can be distinguished. We have investigated methods for doing this in multiply connected BECs in which part of the condensate participates in the atom circuit while another part is left alone so that its phase profile is undisturbed. By releasing the confinement the presence of these topological excitations may be detected via the resulting interference pattern. Using the time--depdendent Gross--Pitaevskii equation, we demonstrate ways in which this may be done for BECs confined in ring--ring and disk--plus--ring traps. We show how to detect vortices, solitons, and phonons. [Preview Abstract] |
Thursday, March 6, 2014 4:18PM - 4:30PM |
W34.00010: Detangling Flat Bands via Fano Structures Joshua Bodyfelt, Sergej Flach, Daniel Leykam, Anton Desyatnikov, Peter Matthies Translationally invariant lattices with flat bands (FB) in the band structure possess irreducible compact localized flat band states (FBS). The number of unit cells involved in one irreducible FBS defines the FB class of the model. For class 1, we transform and detangle the FBS and dispersive states into a Fano lattice. Inverting the scheme, we end up with a continuum of FB models for any FB class. In the case of an on-site disorder potential, the symmetric part lifts the FB degeneracy, keeping compact localization of FBS. The antisymmetric part yields Fano-induced Cauchy tails for the potential felt by the dispersive states. As a result, weak disorder enforces different energy dependent localization length scales, and highly nontrivial mode profiles at the FB energy. Scattering by perturbed FBS can then be understood as Fano resonance. [Preview Abstract] |
Thursday, March 6, 2014 4:30PM - 4:42PM |
W34.00011: Interacting gauge theories in ultracold gases Manuel Valiente, Matthew J. Edmonds, Luis Santos, Gedeminas Juzeliunas, Patrik Ohberg We consider ultracold atoms coupled to a near-resonant laser field, and show how weak interacting -- yet not dynamical -- gauge fields can be induced in the system. The resulting microscopic effective theory corresponds to a physical realization of one-dimensional anyons, while its semiclassical (or mean-field) approximation supports chiral solitons and persistent currents on a ring.\\[4pt] [1] M.J. Edmonds et al., Phys. Rev. Lett. 110, 085301 (2013) [Preview Abstract] |
Thursday, March 6, 2014 4:42PM - 4:54PM |
W34.00012: Three `species' of Schrodinger cat states in an infinite-range spin model Bo Zhao, Cotty Kerridge, David Huse We explore a transverse-field Ising model that exhibits both spontaneous symmetry-breaking and eigenstate thermalization. Within its ferromagnetic phase, the exact eigenstates of the Hamiltonian of any large but finite-sized system are all Schrodinger cat states: coherent linear superpositions of states with `up' and `down' spontaneous magnetization. This model exhibits two dynamical phase transitions {\it within} the ferromagnetic phase between regimes where the motion of the order parameter between `up' and `down' is via quantum tunneling or not, and is always overdamped or not. [Preview Abstract] |
Thursday, March 6, 2014 4:54PM - 5:06PM |
W34.00013: The Hilbert-glass transitions: new universality of temperature-tuned many-body dynamical quantum criticality David Pekker, Gil Refael, Ehud Altman, Eugene Demler, Vadim Oganesyan We study a new class of unconventional critical phenomena that is characterized by singularities only in dynamical quantities and has no thermodynamic signatures. Describing this purely dynamical quantum criticality is technically challenging as understanding the finite-temperature dynamics necessarily requires averaging over a large number of matrix elements between many-body eigenstates. Here we develop a real-space renormalization group method for excited state (RSRG-X) that allows us to overcome this challenge in a large class of models. We characterize a specific example: the 1D disordered transverse field Ising model with generic interactions. While thermodynamic phase transitions are generally forbidden in this model, using RSRG-X we find a finite-temperature dynamical transition between two localized phases. The transition is characterized by non-analyticities in the low frequency heat conductivity and in the long-time (dynamic) spin correlation function. The latter is a consequence of an up-down spin symmetry that results in the appearance of an Edwards-Anderson-like order parameter in one of the localized phases. [Preview Abstract] |
Thursday, March 6, 2014 5:06PM - 5:18PM |
W34.00014: Probing Real-Space and Time-Resolved Correlation Functions with Many-Body Ramsey Interferometry Michael Knap, Adrian Kantian, Thierry Giamarchi, Immanuel Bloch, Mikhail D. Lukin, Eugene Demler We propose to use Ramsey interferometry and single-site addressability, available in synthetic matter such as cold atoms, polar molecules, or trapped ions, to measure real-space and time resolved spin correlation functions. These correlation functions directly probe the excitations of the system, which makes it possible to characterize the underlying many-body states. Moreover, they contain valuable information about phase transitions where they exhibit scale invariance. We explicitly consider examples of the two-dimensional, antiferromagnetic Heisenberg model and the one-dimensional, long-range transverse field Ising model to illustrate the technique. [Preview Abstract] |
Thursday, March 6, 2014 5:18PM - 5:30PM |
W34.00015: Quasiclassical molecular dynamics for the dilute Fermi gas at unitarity Kevin Dusling, Thomas Schafaer We study the dilute Fermi gas at unitarity using molecular dynamics with an effective quantum potential constructed to reproduce the quantum two-body density matrix at unitarity. Results for the equation of state, the pair correlation function and the shear viscosity are presented. These quantities are well understood in the dilute, high temperature, limit. Using molecular dynamics we determine higher order corrections in the diluteness parameter $n\lambda^3$, where $n$ is the density and $\lambda$ is the thermal de Broglie wave length. In the case of the contact density, which parameterizes the short distance behavior of the correlation function, we find that the results of molecular dynamics interpolates between the truncated second and third order virial expansion, and are in excellent agreement with existing T-matrix calculations. For the shear viscosity we reproduce the expected scaling behavior at high temperature, $\eta\sim 1/\lambda^3$, and we determine the leading density dependent correction to this result. [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