Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session P13: Topological and Dynamical Phenomena in AMO Systems |
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Sponsoring Units: DAMOP Chair: Yi Li, Johns Hopkins University Room: 272 |
Wednesday, March 15, 2017 2:30PM - 2:42PM |
P13.00001: Thermometry for Laughlin States of Ultracold Atoms Peter Raum, Vito Scarola Cooling atomic gases into strongly correlated quantum phases requires estimates of the entropy to perform thermometry and establish viability. We construct an ansatz partition function for models of Laughlin states of atomic gases by combining high temperature series expansions with exact diagonalization. Using the ansatz we find that entropies required to observe low energy quasiparticles with bosonic gases are near current cooling capabilities. [Preview Abstract] |
Wednesday, March 15, 2017 2:42PM - 2:54PM |
P13.00002: Quantum melting of a von Neumann lattice of rotating dipole-blockaded bosons in the fractional quantum Hall regime Szu-Cheng Cheng, Shih-Da Jheng, Ting-Wei Chen A novel type of vortex lattice, referred to as a bubble crystal, which was discovered in rapidly rotating Bose gases with dipole-blockaded interactions [Sci. Rep. \textbf{6}, 31801 (2016)]. Bubble crystals are clustered periodically and surrounded by multiple vortices. It was demonstrated that von Neumann lattices well described the physical properties of bubble crystals [Sci. Rep. \textbf{6}, 31801 (2016)]. The behavior and stability of a von Neumann lattice of rotating dipole-blockaded bosons are investigated via finding the elastic moduli and Tkachenko modes of this lattice. We can then calculate the mean square of the displacement vector of von Neumann lattices. The critical filling factor $\upsilon $, above which the lattice state is expected, is evaluated at absolute zero temperature by use of the Lindeman's criterion. We find that the von Neumann lattice is locally stable for $\upsilon $\textless 1, when the integral number of flux quanta per unit cell of the lattice is greater than 3. For rapidly rotating Bose gases with dipole-blockaded interactions, we show that a vortex lattice with an integral number of flux quanta per unit cell can be stable in the fractional quantum Hall regime. [Preview Abstract] |
Wednesday, March 15, 2017 2:54PM - 3:06PM |
P13.00003: Composite fermion basis for two-component Bose gases Marius Meyer, Ola Liabotro The composite fermion (CF) construction is known to produce wave functions that are not necessarily orthogonal, or even linearly independent, after projection. While usually not a practical issue in the quantum Hall regime, we have previously shown that it presents a technical challenge for rotating Bose gases with low angular momentum. These are systems where the CF approach yield surprisingly good approximations to the exact eigenstates of weak short-range interactions, and so solving the problem of linearly dependent wave functions is of interest. It can also be useful for studying CF excitations for fermions. Here we present several ways of constructing a basis for the space of ``simple CF states'' for two-component rotating Bose gases in the lowest Landau level, and prove that they all give a basis. Using the basis, we study the structure of the lowest-lying state using so-called restricted wave functions. We also examine the scaling of the overlap between the exact and CF wave functions at the maximal possible angular momentum for simple states. [Preview Abstract] |
Wednesday, March 15, 2017 3:06PM - 3:18PM |
P13.00004: Deformation of the quantum Hall systems in cold atoms Kuan-Hao Chen, Tin-Lun Ho We study the deformation of bosonic and fermionic quantum Hall states in cold atom systems through changes in their trapping potentials or in the curvature of the underlying spatial manifold. We show how the usual plasma analog can be generalized to study the density profile of these systems, including those with internal degrees of freedom. [Preview Abstract] |
Wednesday, March 15, 2017 3:18PM - 3:30PM |
P13.00005: New parameterization for Quantum Degenerate Systems Jianda Wu, Chao Xu, Congjun Wu We present a new parameterization method describing degenerate quantum systems with maximum allowed parameter space. It is deeply connected to the Grassmannian manifold embedded with specially constructed Pl\"ucker coordinates. We demonstrate that the parameterization naturally leads to Yang monopole holonomy in a special limit at the SO(5) case. Further concrete examples are present to show how the parameterization may expand conventional understandings in topological systems, where possible practical applications are also discussed. [Preview Abstract] |
Wednesday, March 15, 2017 3:30PM - 3:42PM |
P13.00006: New Gauge Invariant in Time-dependent Quantum Degenerate Systems Chao Xu, Jianda Wu, Congjun Wu Quantum dynamical systems have recently received a great deal of attentions, including Floquet, time crystal, and quench problems. Here we present a new non-Abelian gauge invariant which, being a substantial generalization of its Abelian counterpart, emerges in generic time-dependent quantum systems with degenerate instantaneous eigenstates. Its geometric features are demonstrated to play an important role in understanding the topological structure in time-dependent systems. Furthermore, a concrete Hamiltonian is constructed to explicitly demonstrate how the new invariant influences the time evolution in time-dependent systems. The new invariant could be tested by cold Atoms experiments in relevant systems. [Preview Abstract] |
Wednesday, March 15, 2017 3:42PM - 3:54PM |
P13.00007: Zeno Hall effect Zongping Gong, Sho Higashikawa, Masahito Ueda The quantum Zeno effect and the Hall effect are two seemingly unrelated fundamental physical phenonmena, yet we find that the former can give rise to the latter by tailoring the Hilbert space of a two-dimensional lattice system into a single Bloch band with a nonzero Berry curvature. Consequently, a wave packet undergoes transverse motion in response to a potential gradient. We call such a phenomenon the Zeno Hall effect to be distinguished from other Hall effects in the quantum Zeno origin. Our findings provide a general protocol to engineer flat bands. We also propose an experimental implementation with cold atoms in an optical lattice. [Preview Abstract] |
Wednesday, March 15, 2017 3:54PM - 4:06PM |
P13.00008: The benefit of interactions in the manifestation of topological edge states in spinor Bose systems with soft boundaries Bogdan Galilo, Derek K. K. Lee, Ryan Barnett We investigate the Kane-Mele model for spin 1 ultra-cold Bose atoms. We show that in the presence of a harmonic trap, interactions can facilitate the emergence of topological edge states by screening the effect of the trap. A sharpening of boundaries around the screening radius occurs. We find that for sufficiently weak harmonic traps the number of edge states is higher than in the commonly adopted case of hard-wall boundary conditions. Our calculations show that the number of edge states is determined by the ratio of the energy gap and the product of the Thomas-Fermi radius, harmonic frequency, atomic mass, and lattice constant. The latter determines the slope of the screened potential and forms a characteristic energy scale at the boundary. Our results can be extended to other lattice models of interacting spin-1 boson particles. [Preview Abstract] |
Wednesday, March 15, 2017 4:06PM - 4:18PM |
P13.00009: Discovery of an Unexpected Liquid Phase in the Periodically Driven Paul Trap Daniel Weiss, Yunseong Nam, Reinhold Blümel Charged particles confined in a Paul trap generally exist in one of two phases: the cloud phase - characterized by rf heating and chaotic dynamics - and the crystal phase - defined stroboscopically as a period-1 fixed point in phase space, where there is no heating. Here we present evidence supporting the existence of a liquid phase. In contrast to the cloud state, the liquid phase is characterized by an almost negligible heating rate. [Preview Abstract] |
Wednesday, March 15, 2017 4:18PM - 4:30PM |
P13.00010: Relaxations in few-body systems Yasushi Kondo We have been interested in relaxation and its suppression from the view point of quantum information processing~[1, 2]. Relaxation of a system may be interpreted as a one-way flow of information from this system to an environment of which degrees of freedom is infinite. We realize two controlled relaxations of a spin (our system) in a not-so-large molecule by using liquid-state NMR techniques. Our information is the coherence of the spin. In the first experiment, an information flow is controlled by introducing a wall that absorbs the information. We realize this wall by using an external stochastic field generated by magnetic impurities added in solvent. In the second one, we employ a molecule of which structure is very asymmetric, such as DSS (4,4-dimethyl-4-silapentane-1-sulfonic acid). Here, the system is a Si-spin in DSS, while the environment is the rest of spins of which number is only 16. The degrees of freedom of this environment is not infinitely large, but may be large enough to pretend to an open one. [1] Y.\ Kondo, et al, J.\ Phys.\ Soc.\ Jpn.\ {\bf 76}, 10 (2007). [2] Y.\ Kondo, et al, New J.\ Phys.\ {\bf 18}, 013033 (2016). [Preview Abstract] |
Wednesday, March 15, 2017 4:30PM - 4:42PM |
P13.00011: Generalized hydrodynamics and non-equilibrium steady states in integrable many-body quantum systems Romain Vasseur, Vir Bulchandani, Christoph Karrasch, Joel Moore The long-time dynamics of thermalizing many-body quantum systems can typically be described in terms of a conventional hydrodynamics picture that results from the decay of all but a few slow modes associated with standard conservation laws (such as particle number, energy, or momentum). However, hydrodynamics is expected to fail for integrable systems that are characterized by an infinite number of conservation laws, leading to unconventional transport properties and to complex non-equilibrium states beyond the traditional dogma of statistical mechanics. In this talk, I will describe recent attempts to understand such stationary states far from equilibrium using a generalized hydrodynamics picture. I will discuss the consistency of ``Bethe--Boltzmann'' kinetic equations with linear response Drude weights and with density-matrix renormalization group calculations. [Preview Abstract] |
Wednesday, March 15, 2017 4:42PM - 4:54PM |
P13.00012: Exactly solvable many-body driven-dissipative systems Mohammad F. Maghrebi, Michael Foss-Feig, Jeremy T. Young, Victor V. Albert, Alexey V. Gorshkov Non-equilibrium driven-dissipative systems are characterized by a fast external drive as well as a coupling to a dissipative bath. The vast range of experimental platforms capable of realizing such systems, specifically experiments with ultracold matter, has brought many open questions about the nature of their steady states and dynamics into the spotlight.~ In this talk, I identify a general class of many-body driven-dissipative systems with dissipation that does not commute with the Hamiltonian, but which nevertheless admit an exact solution. I show that the evolution of the reduced density matrix in any subspace of the system will only depend on the subsystem and its neighboring sites; however, the dynamics is not reducible to that of smaller subsystems. Under generic assumptions, I also argue that the dissipative gap remains finite, thereby preventing a dissipative phase transition in this class of models.~ [Preview Abstract] |
Wednesday, March 15, 2017 4:54PM - 5:06PM |
P13.00013: Dissipation-Induced Ordering in a Non-Markovian Open Dicke Model Marco Schiro, Orazio Scarlatella We consider the Dicke model, describing an ensemble of N two-level systems interacting with a light field, and investigate the effect of a non-Markovian environment. We find, in the thermodynamic limit, a dissipation-induced superradiant phase transition as the coupling to the bath is increased, in striking qualitative contrast with the result obtained in a Markovian, memory-less, environment. We argue this to be the mean field limit of a genuine dissipative quantum phase transition, of spin-boson nature, existing in this system for any finite N. [Preview Abstract] |
Wednesday, March 15, 2017 5:06PM - 5:18PM |
P13.00014: Scrambling and thermalization behavior of a diffusive system Annabelle Bohrdt, Christian B. Mendl, Manuel Endres, Michael Knap Dynamical correlation functions give valuable insights into the thermalization behavior of a many-body system. We investigate different dynamical correlation functions in the non-integrable one-dimensional Bose-Hubbard model by means of density matrix renormalization group schemes. At high temperatures, well defined quasi-particles cease to exist and the time-ordered Green’s function exhibits rapidly decaying excitations. Out-of-time ordered (OTO) correlators on the other hand have recently been proposed to describe the spread of quantum information, which is not necessarily coupled to the propagation of quasi-particles. Despite the high temperatures, we indeed observe that the OTO correlators display a pronounced linear light-cone. Our numerical analysis moreover reveals that the scrambling of information does not account for the slowest timescale in the thermalization behavior of the system. Instead, conserved quantities cause hydrodynamic long-time tails which decelerate the full thermalization. We furthermore propose two different interferometric schemes to approach the challenge of measuring time-ordered as well as out-of-time ordered dynamical correlation functions in real space in cold atom experiments. [Preview Abstract] |
Wednesday, March 15, 2017 5:18PM - 5:30PM |
P13.00015: Probing non-Hermitian physics with an imaginary potential Jianming Wen, Yanhong Xiao, Peng Peng, Wanxia Cao, Ce Shen, Weizhi Qu, Liang Jiang We report the first experimental realization of anti-parity-time (anti-PT) symmetry [1], a counterpart of conventional PT symmetry [2], in a warm EIT atomic-vapor cell. Using rapid coherence transport via flying atoms, we observe not only essential features of anti-PT symmetry with an unprecedented precision on PT-phase transition, but also introduce a novel dissipative yet coherence coupling mechanism which resembles a pure imaginary potential. With the setting, we further demonstrate some novel phenomena including light refractionless (or unit-refraction) propagation, nonlocal interference between two spatially separated light waves, and anti-PT-assisted four-wave mixing. [1] P. Peng, W. Cao, C. Shen, W. Qu, J. Wen, L. Jiang, and Y. Xiao, Nature Physics, DOI: 10.1038/NPHYS3842 (2016). [2] L. Chang, X. Jiang, S. Hua, C. Yang, J. Wen, L. Jiang, G. Li, G. Wang, and M. Xiao, Nature Photonics \textbf{8}, 524-529 (2014). [Preview Abstract] |
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