Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session B33: Topological and Disorder Physics in AMOFocus Recordings Available
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Sponsoring Units: DAMOP Chair: Axel Pelster, Kaiserslautern Room: McCormick Place W-192C |
Monday, March 14, 2022 11:30AM - 11:42AM |
B33.00001: Continuum and low energy limit of one-dimensional lattice anyons Sebastian Eggert, Axel Pelster, Martin Bonkhoff, Thore Posske, Michael Thorwart, Kevin Jägering We consider interacting abelian anyons on a one-dimensional lattice which can be realized in ultracold gases experiments with density dependent hopping. It is shown that the continuum limit is possible even while maintaining the full topological exchange properties. The theory differs from previous 1D continuous anyon representations since the 2π periodicity of the anyonic phase is maintained, which normally is only possible for 2D anyons with continuous topological exchange. We derive the corresponding low energy Luttinger Liquid theory, which has the hallmark of different velocities for left- and right-moving collective excitations. |
Monday, March 14, 2022 11:42AM - 11:54AM |
B33.00002: Quantum transport evidence of isolated topological nodal-line fermions Hoil Kim, Jong Mok Ok, Seyeong Cha, Bo Gyu Jang, Chang Il Kwon, Yoshimitsu Kohama, Koichi Kindo, Won Joon Cho, Eun Sang Choi, Youn Jung Jo, Woun Kang, Ji Hoon Shim, Keun Su Kim, Jun Sung Kim Topological nodal-line semimetals have been shown interesting anomalous transport responses, dictated by the nontrivial band topology, with rich topological structures. However, their transport signatures have often been masked by the complexity in band crossings or the coexisting topologically trivial states. Here we show that, in slightly hole-doped SrAs3, the single-loop nodal-line states are well-isolated from the trivial states and entirely determine the transport responses. Shubnikov-de Hass oscillations in SrAs3 confirm dominant charge conduction by nodal-line fermions and identify its tubular Fermi surface, thinnest among those of known nodal-line semimetals, and the characteristic smoke-ring-type pseudospin texture. These unique characters of nodal-line fermions lead to the significantly enhanced quantum interference effect, resulting in the largest weak antilocalization contribution to electric conduction among topological semimetals, making the isolated nodal-line fermions in SrAs3 desirable for novel devices based on their topological charge and spin transport. |
Monday, March 14, 2022 11:54AM - 12:06PM |
B33.00003: Time evolution of non-ergodic extended states David A Zarate, Lea F Santos, Eduardo J Torres Increasing onsite disorder in an isolated Heisenberg spin-1/2 chain leads to the transition from chaos to many-body localization. We obtain a semi-analytical expression for the entire evolution of the survival probability in the intermediate region between chaos and localization. This expression captures the quantity's initial power-law decay, as well as the correlation hole and the ramp toward saturation. We find very good agreement with our numerical results. |
Monday, March 14, 2022 12:06PM - 12:18PM |
B33.00004: Strong zero modes in chiral Z3 clock models Saeed Rahmanian Koshkaki, umar javed, Michael Kolodrubetz, Dganit Meidan, Aditi Mitra, Tami Pereg-Barnea The strong zero mode in Z3 clock models, unlike the Z2 models, is expected not to exist throughout the phase diagram even when there are weak edge modes that switch the system between the symmetry-breaking ground states. The strong mode stability in Z3 models away from fine-tuned parameters is yet to be fully characterized. In this work, we investigate the zero-energy edge mode stability and dynamics in the chiral clock model away from the fine-tuned parameters. We show aspects of the predicted stability and map the strong zero mode to the topological edge mode of an SSH-like model through recently developed operator Krylov techniques. Adding interactions, we discuss how the strong mode becomes a long-lived almost strong mode, again using the language of edge state tunneling within the Krylov operator Hamiltonian. |
Monday, March 14, 2022 12:18PM - 12:54PM |
B33.00005: Localization and topology in disordered and quasiperiodic synthetic lattices Invited Speaker: Bryce Gadway Artificial materials based on atoms and photons present unique opportunities to explore aspects of localization and topology. The level of control over such systems has recently been expanded through the introduction of synthetic lattices, wherein tight-binding Hamiltonians can be spectroscopically engineered through the driving of transitions between, e.g., atomic internal states or momentum states. We describe how this spectroscopic approach to Hamiltonian design can be used to create lattice-like systems with tunable disorder and quasiperiodicity, and discuss experimental results on the exploration of parameter-tunable single-particle mobility edges and disorder-induced topology in such systems. |
Monday, March 14, 2022 12:54PM - 1:06PM |
B33.00006: Reservoir-assisted symmetry breaking and coalesced zero-energy modes in an open PT-symmetric Su-Schrieffer-Heeger model Savannah S Garmon, Kenichi Noba We study a parity-time (PT)-symmetric trimer with non-Hermitian strength parameter γ coupled to two semi-infinite Su-Schrieffer-Heeger (SSH) leads. Two zero-energy modes occur, one of which is localized while the other is anti-localized, that have properties in common with SSH edge modes. We demonstrate two types of PT-symmetry breaking. Within the parameter space corresponding to the topologically non-trivial phase of the SSH chains, a gap opens within the broken PT regime of the discrete eigenvalue spectrum. For smaller values of γ, the eigenvalues are embedded in the two SSH bands, becoming destabilized primarily due to the resonance interaction with the continuum. We call this reservoir-assisted PT-symmetry breaking. As γ is increased, the eigenvalues exit the SSH bands and the discrete eigenstates become more strongly localized in the central trimer region. This approximate decoupling results in the discrete spectrum behaving more like the independent trimer, including both a region in which the PT-symmetry is restored (the gap) and a second region in which it is broken again. At the upper edge of the gap, two eigenstates coalesce with the localized zero-energy mode, resulting in a third-order exceptional point that can be detected in the survival probability dynamics. |
Monday, March 14, 2022 1:06PM - 1:18PM |
B33.00007: Effect of Topology on the Anderson Transitions in Non-Hermitian Systems Zhenyu Xiao, Xunlong Luo, Kohei Kawabata, Tomi Ohtsuki, Ryuichi Shindou Using Hermitization, we have proven that critical exponents of the length scale in non-Hermitian systems coincide with the critical exponents in the corresponding Hermitian systems [1]. The correspondence enables us to evaluate critical exponents in Hermitian systems with larger system sizes. Several tight-binding models in non-Hermitian symmetry classes A and AI are studied by transfer matrix method. Accurate critical exponents are obtained and compared with known results in corresponding Hermitian symmetry classes AIII and BDI [2][3]. Based on the numerical results, we propose a topological mechanism that explains a variance of critical exponents in the same Hermitian symmetry class. |
Monday, March 14, 2022 1:18PM - 1:30PM |
B33.00008: Non-Hermitian Many-Body Localization in Coupled Hatano-Nelson Interacting Chains Kuldeep Suthar, Yi-Cheng Wang, Yi-Ping Huang, Jhih-Shih You, Hsiang-Hua Jen The physics of non-Hermitian systems has attracted significant interests in recent years. The phenomena of non-Hermiticity originate from an exchange of energy or particles with environment and leads to several rich properties such as parity-time symmetry breaking, exceptional points unique to non-Hermitian topology etc. Recently, it has been shown that a non-Hermitian system with random disorder or quasiperiodic potential possessing time-reversal symmetry exhibit complex-real transition. In this work, we study the many-body localization in coupled Hatano-Nelson interacting chains. Incontrast to the previous studies of the spinless fermionic system, the two-chain system shows a complex-real transition which does not coincide to the localization transition. Moreover, the critical coupling strength of the transition decreases as the ratio of respective non-reciprocal hoppings varied. We further investigate the two-chain model with gain-loss terms, and study the localization and eigenspectrum properties of the system. Our study opens up a direction towards an exploration of the critical effects of disordered non-Hermitian many-body systems in cold-atom experiments. |
Monday, March 14, 2022 1:30PM - 1:42PM |
B33.00009: Non-Hermitian optical atomic mirror Yi-Cheng Wang, Jhih-Shih You, Hsiang-Hua Jen Explorations of symmetry and topology have led to important breakthroughs in quantum optics, but much richer behaviour arise from the non-Hermitian nature of interactions of light with matter. Recently an optical mirror has been realized by using subwavelength arrays of atomic reflectors, which display the cooperative optical effects resulting from the photon-mediated dipole-dipole interactions. The loss processes associated with free space emission intrinsically endow the optical mirror with capability of carrying and creating a new non-Hermitian platform with unique symmetry and topology. Here we show that exceptional points and bulk Fermi arcs develop from a nondefective degeneracy by lowering the crystal symmetry of a two-dimensional square array of neutral atoms. We find, although the dipole-dipole interaction is reciprocal, the geometry-dependent non-Hermitian skin effect emerges. This phenomenon can be understood as resulting from the interplay of non-Hermiticity and low crystalline symmetry. Furthermore, long-range interactions lead to the anomalous size-dependent skin modes which are localized at a boundary. The long-rang interacting optical mirror provides a genuine paradigm that bridges two of the most active fields, non-Hermitian and topological physics, and opens the door to the observation of a wide range of outstanding phenomena that would be challenging in condensed matter. |
Monday, March 14, 2022 1:42PM - 1:54PM |
B33.00010: Nested spheres description of the N-level Chern number and the generalized Bloch hypersphere Nur Unal, Cameron Kemp, Nigel R Cooper The geometric interpretation of spin 1/2 systems on the Bloch sphere has been appreciated in physics research. While similar notions for larger Hilbert spaces exist in mathematics, they have been less explored for practical usage in condensed matter settings. We characterize a general N-level system by its coherence vector on the higher dimensional generalized Bloch (hyper)sphere, where topological properties take simple forms set by the SU(N) algebra. We present a geometric interpretation for the N-level Chern number in terms of a nested structure comprising N-1 two-spheres, with an exterior two-sphere that provides a useful characterization by playing a primary role in determining the Chern number, which can be directly measured in ultracold atoms via band mapping techniques. By investigating the time evolution directly on the Bloch hypersphere, we develop a tomography scheme involving quenches to extract the full state vector of three-level systems in experiments. Our geometric description opens up a new avenue for the interpretation of the topological classification and the dynamical illustration of multilevel systems, which in turn helps in the design of new experimental probes. |
Monday, March 14, 2022 1:54PM - 2:06PM |
B33.00011: Enhanced superconductivity due to spectrum-wide wavefunction criticality in quasiperiodic and power-law random hopping models Xinghai Zhang, Matthew Foster There has been a surge of interest in quasiperiodic systems, with applications in ultracold atoms, many-body localization, and twisted bilayer systems at larger twist angles. The Aubry-André(AA) model is a canonical example of a 1D quasiperiodic system, and its entire spectrum of single-particle wave functions is critical (multifractal) at the metal-insulator transition (“spectrum-wide criticality”). This strange feature also occurs in the ensemble of power-law random banded matrices (PRBM), and was very recently discovered to occur generically at the 2D surface of 3D topological superconductors [1]. Here we study the interplay of critical wave functions and superconductivity in AA and PRBM models with attractive interactions via self-consistent BCS theory. Spectrum-wide criticality survives the incorporation of attractive interactions, and we show that superconducting pairing is most enhanced for the interaction-dressed spectrum-wide critical condition. Finally, we examine the interplay of Chalker scaling between critical wave functions and the enhancement of pairing in both models. |
Monday, March 14, 2022 2:06PM - 2:18PM |
B33.00012: Second-order nonlinear optics in silicon David Heydari, Mircea Catuneanu, Edwin Ng, Dodd J Gray, Ryan Hamerly, Hideo Mabuchi, Kambiz Jamshidi The ubiquity and scalability of CMOS technologies are hard to ignore. To that end, nonlinear optics is a promising enhancement to this technology, enabling compact sources in the 1.2 to 4 μm wavelength range that are sufficiently affordable, compact, and low power. Efficient transduction of photons via nonlinear optics necessitates second-order material optical nonlinearities, which are identically zero in silicon. Second-order nonlinearities can, however, be induced in silicon via the application of a DC electric field, which has thus far been demonstrated at room temperature. We demonstrate additional proof-of-concept for this technology and provide future roadmaps for its scalability and applicability to quantum information processing. |
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