Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session N61: Precision Many Body Physics II: Topology and Strong CorrelationsFocus
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Sponsoring Units: DCOMP Chair: Sathwik Bharadwaj, Purdue University Room: Room 418 |
Wednesday, March 8, 2023 11:30AM - 12:06PM |
N61.00001: Interacting bosons in periodically modulated optical lattices: realization of a moat band and pre-thermal relaxation in effective Hamiltonians Invited Speaker: Trey Porto We experimentally realize two different effective Hamiltonians for weakly interacting bosons held in periodically modulated optical lattices, both of which are proposed platforms for generating correlated topological states. Since the interactions required for many interesting Floquet-engineered states often lead to heating, we also study heating and equilibration in the modulated lattices. First, by modulating the amplitude of a checkerboard optical lattice, we generate an effective single particle Hamiltonian where the energy displays a continuum of nearly degenerate minima that lie along a circle in reciprocal space. We measure the condensate lifetime and argue that the observed dynamical instability is characteristic of condensates in any moatlike dispersion, including spin-orbit coupled systems. In separate experiments we shake the checkerboard lattice to engineer single particle Hamiltonians with dynamically tunable effective magnetic fields. By quenching the system between different Floquet-induced fields with different equilibrium ground states, we observe Bose re-condensation of quench-excited atoms on time scales faster than global heating due to the drive. These results are promising steps toward generation of correlated states by Hamiltonian modulation, but drive-induced heating (observed here in the weakly interacting limit) is poorly understood in the highly correlated limit and needs to be further studied to determine if such correlates states are realizable. |
Wednesday, March 8, 2023 12:06PM - 12:42PM |
N61.00002: Excitonic topological order in correlated electron-hole bilayers Invited Speaker: Rui-Rui Du Correlation and frustration play essential roles in physics, which gives rise to a variety of exotic quantum phases. We have observed an unconventional excitonic ground state with unequal electron and hole densities in inverted InAs/GaSb bilayers. Here in zero magnetic field (B) a large bulk gap exists encompassing a broad range of density imbalance, accompanied by a gapless edge state that resembles helical transport. Under an increasing perpendicular B the bulk gap persists in the same regime and anomalous plateau of Hall signal appears, demonstrating an evolution from helical-like to chiral-like edge transport. These results point to a spontaneous time-reversal symmetry (TRS) breaking topological excitonic insulator with density imbalance. Theoretically, we find that, strong frustration from density imbalance leads to a moat band for excitons (similar to a flat band). This generates an excitonic topological order (ETO) which can be represented by a composite fermion (a boson attached to one Chern-Simons flux) state at filling factor 1. The ETO consistently explains all our experimental observations. Our work could open up a new direction for research on topological and correlated bosonic system in solid states. |
Wednesday, March 8, 2023 12:42PM - 12:54PM |
N61.00003: Ballistic transport and persistent circulation in a polariton ring condensate Qi Yao, Evgeny Sedov, Shouvik Mukherjee, Jonathan C Beaumariage, Burcu OZDEN, Hassan A Alnatah, Kenneth W West, Loren N Pfeiffer, Alexey Kavokin, David W Snoke Exciton-polaritons are quasiparticles that are a superpositions of excitons and photons. In a microcavity, exciton-polaritons have an effective mass and can form a Bose-Einstein condensate (BEC). Experimentally, this condensate is generated by pumping light into a microcavity structure with quantum wells at the antinodes of the light field. The features of the polaritons are carried by the light they emit, so we can detect those by using conventional optical methods. |
Wednesday, March 8, 2023 12:54PM - 1:06PM |
N61.00004: Coherent Fraction of a Uniform Two-dimensional Bose Gas in Thermal Equilibrium Hassan A Alnatah, David W Snoke, Loren N Pfeiffer, Kirk W Baldwin Strong coupling of cavity photons and quantum-well excitons gives rise to new bosonic quasiparticles called exciton-polaritons. We have measured the distribution function of a homogenous polariton gas and show that it is well described by a Bose-Einstein distribution, indicating that the polariton gas is in thermal equilibrium. In addition, we measure the coherent fraction of the polariton gas by creating the interference pattern of the light emitted from the gas overlapped with its mirror image. The visibility of the interference fringes gives a direct measurement of the coherent fraction of the polariton gas as a function of the total polariton density. This allows comparison of our results with theoretical predictions of the coherent fraction of an interacting 2D Bose gas. |
Wednesday, March 8, 2023 1:06PM - 1:18PM |
N61.00005: Non-reciprocity as a probe of exotic quantum many-body states in iron-based superconductors Yuki Sato, Ilya Belopolski, Ryota Watanabe, Ryutaro Yoshimi, Minoru Kawamura, Atsushi Tsukazaki, Naoya Kanazawa, Kei S Takahashi, Masashi Kawasaki, Yoshinori Tokura The interplay of broken inversion symmetry, magnetic order, electronic nematicity and superconducting instability is expected to drive exotic electronic states, such as spin-triplet pairing, nematic superconductivity, and Majorana edge mode. Materials with neither inversion nor time reversal symmetry are also subject to exhibit non-reciprocal transport phenomena, where currents flowing forward and backward are inequivalent. Although such effect has been investigated in mostly 2-dimensional polar superconductors, it remains little explored whether it can be found in a system where time reversal symmetry is broken through the proximity effect from an adjacent ferromagnetic material. Here by using novel MBE synthesis techniques, we develop epitaxial interface of ferromagnet and iron-based superconductors such as Fe(Se,Te). We show how non-reciprocity found in our devices reflects exotic quantum many-body states in iron-based superconductors. |
Wednesday, March 8, 2023 1:18PM - 1:30PM |
N61.00006: Multiloop Quantum Field Theory of the Electron Liquid Kun Chen The electron liquid in simple metals is a charged Fermi liquid with relatively strong interactions. We show numerical evidence that the Landau quasiparticle picture in such Fermi liquid can be extended to the entire Fermi volume. This observation motivates a UV-complete renormalized field theory of the electron liquid which provides a quasiparticle point of view of the many-electron problem. Solving the field theory with state-of-the-art numerical techniques reveals emergent BCS superconductivity that is beyond the Kohn-Luttinger mechanism. The field theory provides a systematic foundation for designing ab-initio electronic structure methods beyond the GW approximation. |
Wednesday, March 8, 2023 1:30PM - 1:42PM Author not Attending |
N61.00007: Controlling the numerical sign problem via complex path integration in a simple bosonic model of quantum frustration. Snir Gazit, Elyasaf Cohen, Andrei Alexandru Geometric frustration is a paradigmatic instance of the numerical sign problem in condensed matter systems, where the presence of non-positive or, more generally, complex quantum amplitudes renders quantum Monte Carlo techniques uncontrolled. This work employs the recently introduced complex path integration (CPI) method to overcome this obstruction in a simple geometrically frustrated bosonic model defined on a triangular chain with negative hopping amplitudes at a finite chemical potential. Within the CPI method, the path integral is deformed into a complex plane manifold, which is set by the holomorphic flow. Remarkably, we find a dramatic reduction in the severity of the numerical sign problem. This progress allows us to accurately determine the many-body ground state properties away from commensurate fillings. Specifically, we tune an order-disorder quantum phase transition by varying the chemical potential and present the evolution of various observables along the transition, including the vanishing many-body gap, boson particle number, and condensate fraction. Extensions of our work and refinements of the CPI method will be discussed. |
Wednesday, March 8, 2023 1:42PM - 1:54PM |
N61.00008: Electronic excited states from quantum embedding Chenghan Li, Garnet K Chan The density matrix embedding theory (DMET) has shown success to describe the many-body electronic ground state of strongly correlated systems. Herein, we present a new method for computing excited states in the framework of DMET using linear response theory. We demonstrate how our method can be applied to the Hubbard model and hydrogen chain systems. |
Wednesday, March 8, 2023 1:54PM - 2:06PM |
N61.00009: Approximate Hamiltonian Reconstruction from Undercomplete Operator Bases Alexander Jacoby We examine the effects of incomplete operator bases on the so-called correlation matrix Hamiltonian reconstruction technique [Qi and Ranard; Quantum 3, 159 (2019)]. Our study is motivated by the experimental inaccessibility of many correlators which are needed for an exact reconstruction. We address the fidelity of approximate reconstructions and try to understand when a reconstruction attempt will go from approximately correct to wholly incorrect. We also derive a perturbative expression that relates the degree of failure in the approximate method to the magnitude of the missing terms in the reconstructed Hamiltonian. Our model systems include simple spin chains with non-local but decaying couplings (e.g. the Haldane-Shastry model) and those with higher spin exchanges with diminishing coefficients (like in the Mott limit of the Hubbard model). In the former case, we explore truncations that remove the long-distance or high-momentum physics. In the latter case, we truncate the higher spin exchanges. |
Wednesday, March 8, 2023 2:06PM - 2:18PM |
N61.00010: L-shape NLCE expansion for square-lattice models Mahmoud Abdelshafy, Marcos Rigol We introduce a Numerical Linked Cluster Expansion (NLCE) based on L-shaped clusters in the square lattice. NLCE expansions are known to converge – exponentially fast in the size of the clusters – in unordered phases. In ordered phases, even if the correlation length is finite (such as in the classical Ising model in the square lattice), NLCE expansions based on bonds or sites fail to converge. We show that the expansion proposed in this study, however, converges (exponentially fast in the size of the clusters) as one approaches the ground state of the classical Ising model and the transverse field Ising model. Furthermore, we show that studying thermodynamic properties of those models below and above the transition allows us to bound the critical region in which the phase transition occurs. |
Wednesday, March 8, 2023 2:18PM - 2:30PM |
N61.00011: Deconstructing entanglement in the 1D Bose-Hubbard model: bipartite fluctuations and symmetry-resolved entanglement Emanuel Casiano-Diaz, Chris M Herdman, Adrian G Del Maestro In quantum many-body systems of itinerant particles, the entanglement between spatial subregions comprises entanglement due to particle fluctuations between subregions, and the symmetry-resolved entanglement–the entanglement within each subsystem particle number sector. Here we present a numerical study of this entanglement structure in the Bose-Hubbard model in one spatial dimension, a paradigmatic and experimentally relevant itinerant boson system. Using a path integral quantum Monte Carlo method, we have performed a numerical analysis of the subsystem scaling and finite-size scaling of the Rényi entanglement entropy, bipartite number fluctuations, and symmetry resolved Rényi entanglement entropy in the 1D Bose-Hubbard ground state. We demonstrate the dependence of these scalings on the Luttinger parameter in the superfluid phase, as predicted by Luttinger liquid theory. Additionally, we explore the scaling of the operationally accessible entanglement near the critical point. |
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