Bulletin of the American Physical Society
54th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 68, Number 7
Monday–Friday, June 5–9, 2023; Spokane, Washington
Session X08: Quantum Phases in Optical Lattices III |
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Chair: Kaden Hazzard, Rice Room: 206 C |
Friday, June 9, 2023 8:00AM - 8:12AM |
X08.00001: Numerical study of the t-J model in mixed dimensions Henning Schloemer, Timon A Hilker, Immanuel Bloch, Ulrich J Schollwoeck, Fabian Grusdt, Annabelle Bohrdt Unveiling the microscopic origins of quantum phases dominated by the interplay of spin and motional degrees of freedom constitutes one of the central challenges in strongly correlated many-body physics. When holes move through an antiferromagnetic spin background, they displace the positions of spins, which in turn induces effective frustration in the magnetic environment. This competition in paradigmatic Hamiltonians like the Fermi-Hubbard and t-J model gives rise to a plethora of many-body phases, many of which still lack microscopic understanding. In this talk, we present numerical studies of the t-J model in mixed dimension, where charge carriers are restricted to move only in one direction, whereas magnetic SU(2) interactions are two-dimensional. At low temperatures, we find that hidden spin correlations lead to a remarkably resilient stripe phase featuring incommensurate magnetic order. At elevated temperatures, where charge carries effectively move freely through the spin background, we use Hamiltonian reconstruction schemes to recover effective spin-Hamiltonians after detaching the magnetic background from dominant charge fluctuations. This enables us to precisely quantify the magnetic frustration in the spin background induced by the motion of the holes. We demonstrate that the spin background is driven into a highly frustrated spin liquid regime, reminiscent of Anderson's resonating valence bond paradigm in doped cuprates. With recent advances in quantum gas microscopy to mixed dimensions, our study enables an unprecedented microscopic perspective on the doped Hubbard model. |
Friday, June 9, 2023 8:12AM - 8:24AM |
X08.00002: Effects of interaction in the kicked Auby-André-Harper model Toshihiko Shimasaki, Hasan Kondakci, Yifei Bai, Jared E Pagett, Peter Dotti, Peter Tsung-Cheng, Tarun Grover, David M Weld
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Friday, June 9, 2023 8:24AM - 8:36AM |
X08.00003: The number entropy as an accessible measure to detect transport and topological phases Jesko Sirker For a system with particle number conservation, the entanglement entropy of a subsystem can be split into configurational and number entropy. While a measurement of the entanglement entropy requires a full quantum tomography, the number entropy is based on particle distributions alone and accessible, for example, via single site spectroscopy. Here I show that in equilibrium the number entropy can be used as indicator for topological phase transitions in systems with symmetry protected topological order. Furthermore, after a quantum quench, the number entropy shows whether or not particles spread through the system or remain localized. Our results indicate, in particular, that one of the widely studied models for many-body localization (MBL) - the spin-1/2 Heisenberg chain with random magnetic fields - never localizes for finite interactions and disorder strengths which are numerically accessible. This is in contrast to earlier studies which predicted an MBL transition and calls into question whether non-trivial MBL phases exist at all. |
Friday, June 9, 2023 8:36AM - 8:48AM |
X08.00004: Nonequilibrium dynamics of ultracold bosons in an optical quasicrystal Bo Song, Shaurya A Bhave, Lee C Reeve, Emmanuel Gottlob, Ulrich Schneider In this talk, I will discuss the dynamics of ultracold bosons after quenches across the Bose glass transition in an optical quasicrystal. We observe two distinct oscillatory behaviors depending on the direction of the quench: for the quench from the superfluid to Bose glass regime, the dynamics mainly depend on the disorder strength, whereas they are dominated by the tunneling rate for the reverse quench. Moreover, we investigate the coherence of the system following a fast sweep from an initial superfluid to different final lattice depths and experimentally monitor the change of the matter-wave interference. The Bose glass transition is also reflected by how fast the system loses coherence after the sweep, in good agreement with both the phase coherence measurement and theoretical simulation. Our findings using quasicrystals pave the way for exploring many-body localization and thermalization in (quasi-)disordered materials. |
Friday, June 9, 2023 8:48AM - 9:00AM |
X08.00005: Ground state correlations in spin-polarized attractive fermions on optical lattices Ettore Vitali, Shiwei Zhang, Peter Rosenberg, Dhan-Ruzzle Bautista We compute ground state correlations in a system of spin-polarized cold atoms moving on a two-dimensional optical lattice. We focus on the the bulk limit by leveraging an interface between correlated Quantum Monte Carlo techniques and Hartree-Fock-Bogoliubov calculations. Our recent methodological advances allow us to simulate lattices hosting nearly 500 atoms, which helps us minimize finite-size effects. We systematically explore the high density and small spin polarization regime, which is believed to be most favorable to the emergence of the elusive Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superfluid phase. We find clear evidence of FFLO order, which appears to be part of an intricate coexistence of long-range orders. We also explore the effects of introducing spin-orbit coupling, which opens the possibility to observe topological superfluids, with intriguing connection with Majorana fermions. |
Friday, June 9, 2023 9:00AM - 9:12AM |
X08.00006: Invisible flat bands on a topological chiral edge Youjiang Xu, Irakli Titvinidze, Walter Hofstetter We prove that invisible bands associated with zeros of the single-particle Green's function exist ubiquitously at topological interfaces of two-dimensional Chern insulators, dual to the chiral edge/domain-wall modes. We verify this statement in a repulsive Hubbard model with a topological flat band, using real-space dynamical mean-field theory to study the domain walls of its ferromagnetic ground state. Moreover, our numerical results show that the chiral modes are split into branches due to the interaction and that the branches are connected by invisible flat bands. Our work provides deeper insight into interacting topological systems. |
Friday, June 9, 2023 9:12AM - 9:24AM |
X08.00007: SU(3) Fermi-Hubbard Model with Spin Flavor-imbalance Zewen Zhang, Eduardo Ibarra Garcia Padilla, Kevin Zheng, Chunhan Feng, Richard T Scalettar, Kaden Hazzard Motivated by ongoing experiments with alkaline-earth atoms in optical lattices, we investigate the phases of the square lattice SU(3) Fermi-Hubbard model with spin flavor imbalance using Hartree-Fock theory, focusing on the case with one-atom per site average density. Previous calculations on the flavor-balanced system predict the existence of a Mott transition and ordered phases in the strong-interaction limit. Our results suggest that at intermediate interaction strengths, multiple new magnetic and density orders appear. We show that these magnetic ordered phases are robust at small spin flavor imbalance, and that new phases appear upon large flavor imbalance. The mean-field results provide distinctive signatures to search for with ongoing experiments using quantum gas microscopes. |
Friday, June 9, 2023 9:24AM - 9:36AM |
X08.00008: Reversal of quantised Hall drifts at non-interacting and interacting topological boundaries Zijie Zhu, Marius Gachter, Anne-Sophie Walter, Konrad Viebahn, Tilman Esslinger Boundaries between topologically distinct materials give rise to gapless edge modes whose robustness is fundamentally and technologically relevant. Therefore, it is crucial to gain a better understanding of topological edge states, both regarding their transport properties as well as their response to interparticle interactions. Here, we experimentally study quantised Hall drifts in a harmonically confined topological pump of non-interacting and interacting ultracold fermionic atoms. We find that quantised drifts halt and reverse their direction when the atoms reach a critical slope of the confining potential, revealing the presence of a topological boundary. The drift reversal corresponds to a band transfer between a band with Chern number C = +1 and a band with C = -1 via a gapless edge mode, in agreement with the bulk-edge correspondence for non-interacting particles. We establish that a non-zero repulsive Hubbard interaction leads to the emergence of an additional edge in the system, relying on a purely interaction-induced mechanism, in which pairs of fermions are split. |
Friday, June 9, 2023 9:36AM - 9:48AM |
X08.00009: Signatures of many-body localization in a two-dimensional lattice of ultracold polar molecules with disordered filling Timothy J Harris, Andrew J Groszek, Arghavan Safavi-Naini, Matthew J Davis In this talk, we present our work exploring many-body localization (MBL) in systems of ultracold polar molecules in two-dimensional optical lattices. Specifically, we investigate a novel form of ergodicity breaking that arises in systems of ultracold polar molecules due to non-unit lattice fillings. We study the scenario where two well isolated rotational states form an effective spin-1/2 degree of freedom, allowing the molecules to realise a dipolar spin-1/2 Hamiltonian with microscopic parameters tunable via precise control of an external DC electric field. We perform large-scale exact diagonalization simulations to explore the non-equilibrium dynamics and eigenstate properties for systems of up to 16 molecules at 50% lattice filling. We observe several key signatures of MBL as the relative strength of the spin-density interactions is increased, including retention of initial state memory in the system’s long-time dynamics and logarithmic growth of bipartite entanglement entropy. Additionally, we find evidence for divergent entanglement entropy fluctuations close to the critical disorder strength Wc. We extract an estimate for Wc and the critical exponents of the MBL transition in the thermodynamic limit via finite-size scaling analysis. We demonstrate that the results of our dynamical simulations are consistent with an observed crossover behviour in the level-spacing statistics of the many-body Hamiltonian, which is a well known indicator of the thermal to MBL phase transition. Our results are realisable in current molecular quantum gas microscope experiments, and we discuss possible experimental considerations. Our proposal paves the way for studies of many-body localization in higher-dimensional dipolar spin models and highlights the potential for quantum simulation of non-equilibrium dynamics in current state of-the-art ultracold polar molecule platforms. |
Friday, June 9, 2023 9:48AM - 10:00AM |
X08.00010: Feshbach resonances of doped holes in an antiferromagnet Lukas Homeier, Annabelle Bohrdt, Eugene Demler, Fabian Grusdt Feshbach resonances between neutral atoms are a powerful tool in modern ultracold atom experiments because they mediate strong interactions between otherwise only weakly interacting objects. Here, we extend the idea of Feshbach resonances to the low-energy emergent quasiparticles of a strongly correlated background. We argue that dopants in the antiferromagnetic, Mott insulating phase of the Fermi-Hubbard model form a well-defined multi-channel model. This allows us to show that the interaction is dominated by two channels yielding d-wave scattering between magnetic polarons, which we derive ab initio from geometric string theory in the t-J model. In the low doping regime, the effective interactions result in a d-wave BCS superconductor of magnetic polarons. This constitutes a new type of pairing mechanism, which potentially plays an important role for high-Tc superconductivity in cuprates. |
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