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 K29: Strongly Correlated Systems, Including Quantum Fluids and Solids VII |
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Sponsoring Units: DCMP Chair: Maria Tikhanovskaya, Harvard University Room: Room 221 |
Tuesday, March 7, 2023 3:00PM - 3:12PM |
K29.00001: Perturbative non-Fermi liquids from bosonization Umang B Mehta, Dam T Son, Luca V Delacretaz, Yi-Hsien Du We use the nonlinear Fermi surface bosonization of [Phys.Rev.Research 4, 033131] to develop new perturbative schemes to study non-Fermi liquids. The bosonized formalism eliminates the need for decomposing the Fermi surface into patches, and allows for a systematic analysis of the consequences of Fermi surface curvature as well as nonlinearities from the dispersion relation in non-Fermi liquids. |
Tuesday, March 7, 2023 3:12PM - 3:24PM |
K29.00002: Vortex Fermi Liquid and Strongly Correlated Quantum Bad Metal Nayan E Myerson-Jain, Chao-Ming Jian, Cenke Xu The semiclassical description of two-dimensional metals based on the quasiparticle picture suggests that the resistivity of a 2d metal is universally bounded by the Mott-Ioffe-Regal (MIR) limit, at the order of h/e2. If a system remains metallic while its resistivity is beyond the MIR limit, it is referred to as a "bad metal", which challenges our theoretical understanding as the very notion of quasiparticles is invalidated. The description of the system becomes even more challenging when the electrons are strongly correlated. We construct a concrete example of such a strongly correlated bad metal where charged vortices, that serve as dual fermionic degrees of freedom, form a Fermi surface. We demonstrate that at zero and low temperature, the system has a finite resistivity much larger than the MIR limit, and doping away from half-filling generates a small Drude weight in the optical conductivity. |
Tuesday, March 7, 2023 3:24PM - 3:36PM |
K29.00003: Entanglement Entropy in Large-N Theories Siqi Shao, Yashar Komijani Entanglement is one of the central concepts in quantum systems and is characterized by various moments of reduced density matrix, including Renyi and von Neumann entanglement entropies. |
Tuesday, March 7, 2023 3:36PM - 3:48PM Author not Attending |
K29.00004: Many-body quantum chaos in a non-Fermi liquid model with spatially random interactions. Maria Tikhanovskaya, Subir Sachdev, Aavishkar A Patel A description of strange metal states is crucial for understanding strong electron correlations in important materials such as high Tc superconductors and twisted bilayer graphene. One of the viable theories for strange metals is a two-dimensional model of critical Fermi surfaces in the presence of spatially random interactions. The model displays T-linear resistivity at temperatures T→0, which is the defining feature of strange metal behavior, along with other experimentally observed features. In addition to transport properties, it is also important to understand relaxational and thermalization phenomena in strange metals, which shed light on their non-equilibrium properties. To describe a portion of these, we compute out-of-time ordered correlation functions (OTOCs) of fermion operators. We show that the presence of a residual resistivity, often seen in experiments, induces an emergent integrability at low energies, slowing down the growth rate of OTOCs from the maximum possible value of 2πT as T→0, despite the linear T-dependence of the resistivity and the seeming absence of quasiparticles. |
Tuesday, March 7, 2023 3:48PM - 4:00PM |
K29.00005: Broken Luttinger theorem in the two dimensional Fermi Hubbard model Sayantan Roy, Nandini Trivedi, Thereza Paiva, Abhisek Samanta We study the validity of Luttinger's theorem in the two dimensional repulsive Fermi Hubbard model, the parent Hamiltonian for cuprate superconductors, as a function of doping. Using Determinant Quantum Monte Carlo (DQMC) simulations, we compute the single-particle spectral functions and study the Fermi surface of the interacting system. As one approaches the Mott insulating limit, there is a critical doping where the Fermi surface shows a deviation from the Luttinger's volume even in absence of any other broken symmetry. We also conduct a parton mean-field construction (in presence of double occupancies and holes) starting from an effective low-energy Hamiltonian in the large interaction limit, and calculate the Fermi surface of the low-energy Hamiltonian. Our study is also supplemented by the calculation of different transport quantities, like DC Hall coefficient and Seebeck coefficient that capture this phenomenon. |
Tuesday, March 7, 2023 4:00PM - 4:12PM |
K29.00006: Collective density fluctuations of strange metals with critical Fermi surfaces Xuepeng Wang, Debanjan Chowdhury Recent spectroscopic measurements in a number of strongly correlated metals that exhibit non-Fermi liquid like properties have observed evidence of anomalous frequency and momentumdependent charge-density fluctuations. Specifically, in the strange metallic regime of the cuprate superconductors, there is a featureless particle-hole continuum exhibiting unusual power-laws, and experiments suggest that the plasmon mode decays into this continuum in a manner that is distinct from the expectations of conventional Fermi liquid theory. Inspired by these new experimental developments, we address the nature of low-energy collective modes and the particlehole continua for different "solvable" lattice models of non-Fermi liquids that host a critical Fermi surface — a sharp electronic Fermi surface without any low-energy electronic quasiparticles. We scrutinize theoretically the possible existence of a long-lived zero-sound mode, which is renormalized to the plasma frequency in the presence of long-ranged coulomb interactions, and its decay into the continuum over a wide range of frequencies and momenta. Quite remarkably, some of the models analyzed here can account for certain aspects of the universal experimental observations, that clearly lie beyond the purview of standard Fermi liquid theory. |
Tuesday, March 7, 2023 4:12PM - 4:24PM |
K29.00007: Shot noise in correlated electron systems Yiming Wang, Chandan Setty, Shouvik Sur, Qimiao Si Shot noise is a powerful tool to investigate strong correlations in quantum materials [1]. It probes fluctuations of the electric current, and has been employed in the measurement of the elementary charge carried by quasiparticles. In this work we study quantum shot noise in a correlated diffusive metal by constructing a Boltzmann transport equation suitable for the regime of strong correlations. This allows us to address the general effect of electron correlations on the Fano factor, the ratio of the current noise to the current in the DC limit. Calculations of the Fano factor in specific correlated models will also be reported. We discuss the relevance of our results to recent shot noise experiments in the strange-metal regime of a quantum critical heavy fermion metal YbRh2Si2 [2]. |
Tuesday, March 7, 2023 4:24PM - 4:36PM |
K29.00008: Superconductivity and dephasing in a two-dimensional disordered non-Fermi liquid Tsz Chun Wu, Patrick A Lee, Matthew S Foster We study superconductivity and dephasing in a two-dimensional disordered marginal Fermi liquid. We consider a system with N flavors of fermions coupled to SU(N) critical bosons. At the saddle point level, the bosonic propagator acquires a quantum relaxational form, which consequently induces a marginal Fermi liquid self-energy for the fermions that destroys quasiparticles. Although quasiparticles are no longer well-defined, quantum coherence can surprisingly survive and manifest itself through interference of collective excitations. Motivated by the survival of phase coherence, we explore the interplay between Cooperons and critical bosons on superconductivity. At the semiclassical level, the transition temperature Tc is suppressed because of the marginal Fermi liquid self-energy. Interestingly, interactions between Cooperons and the critical bosons can nevertheless enhance Tc through quantum interference. We also examine the effect of dephasing. We find that the dephasing rate saturates very quickly as temperature increases due to the quantum relaxational bosons and that weak localization is therefore strongly suppressed. |
Tuesday, March 7, 2023 4:36PM - 4:48PM |
K29.00009: Renormalization Group for a Mott Quartic fixed point Jinchao Zhao Fermi liquid theory can be viewed as a fixed point because of the stability of the Fermi surface to short-range repulsive interactions. The only instability is pairing in the Cooper channel. In the context of the cuprates, a similar question arises: Is there a fixed point that captures Mott physics and the underlying superconducting instability? This work builds on recent scaling and symmetry arguments which establish that Mott physics is controlled by a fixed point that breaks the $Z_2$ symmetry of a Fermi liquid[Huang extit{et al}., Nat. Phys. extbf{18}, 511 (2022)]. We demonstrate this here by a renormalization argument starting from the Hatsugai-Kohmoto model as the zeroth-order action. Considering a d-dimensional(d>2) system with a Mott transition controlled by the HK interaction, we show that at tree-level scaling analysis, the only relevant perturbation is of the superconducting(BCS) type. We also derive the RG equations at one-loop for the two-particle vertex function and show that indeed the HK model represents a true low-temperature fixed point for Mott physics. That is, interactions of the Hubbard type (modulo magnetism) do not destroy the Luttinger surface. |
Tuesday, March 7, 2023 4:48PM - 5:00PM |
K29.00010: Stability of Highly Entangled Metallic States Inho Song, Minsoo Park, Hanbit Oh, Eun-Gook Moon We study the stability of a class of highly entangled metallic states, such as orthogonal metals |
Tuesday, March 7, 2023 5:00PM - 5:12PM |
K29.00011: Moiré-Mott insulators in transition metal dichalcogenides: Spin liquids and doping Urban F Seifert, Zhenhao Song, Zhu-Xi Luo, Leon Balents Moiré heterostructures of transition metal dichalcogenides (TMD) have been shown to give rise to correlated insulating states at fractional fillings, forming self-organized charge lattices. The combination of spin-orbit coupling and moiré modulation can lead pseudomagnetic fields and associated fluxes patterns for electrons. We explore the possibility of spin-liquid states in these systems. We further discuss the effects of doping these correlated insulating states at fractional fillings. |
Tuesday, March 7, 2023 5:12PM - 5:24PM |
K29.00012: Nagaoka Ferromagnetism of 3x3 Dopant Arrays in Silicon Yan Li, Garnett W Bryant Nagaoka ferromagnetism (NF) is a long-predicted example of ferromagnetism in the Hubbard model and has been studied theoretically for many years. Recently, NF was realized experimentally in quantum-dots systems for 2x2 plaquettes. NF occurs when there is one fewer electron than half-filling and a large on-site Coulomb repulsion which does not arise naturally in materials. Due to the atomically precise fabrication of dopant arrays in Si, it is possible to engineer complex geometries and make highly controllable systems. These properties make them good candidates to study NF in different array geometries. Here we describe theoretical simulations done for 3x3 arrays of dopants in Si, such as the dopant arrays studied at NIST, and look for the emergence of NF. Unlike 2x2 plaquettes, we find no evidence for Nagaoka ferromagnetism in perfect 3x3 arrays. We show that the antiferromagnetic state is always the ground state in perfect 3x3 arrays because the energy cost to separate opposite spin electrons in suppressed in arrays larger 2x2. Theoretical simulations are done for arrays more constrained either by special geometries or disorder to see if additional localization induces NF. Our results define possible experiments to hunt for Nagaoka ferromagnetism. |
Tuesday, March 7, 2023 5:24PM - 5:36PM |
K29.00013: The interplay of charge-4e and nematic order: a study based on generalized XY model Xuan Zou, Zhouquan Wan, Hong Yao Previous studies suggested that charge-4e superconductivity can emerge from a nematic superconductor by the proliferation of nematic vortices. In this work, we study a generalized XY model whose ground state breaks U(1) and rotation symmetry simultaneously as with the nematic superconductor. Upon increasing temperature, we show that quasi-long range order of U(1) charge $e^{i heta}$ is first destroyed with $e^{i2 heta}$ (charge-4e order parameter) remaining quasi-long range ordered. Interestingly, at the time when $e^{i heta}$ is disordered, the nematic long-range order phase changes into a critical phase with nematic power-law correlation. With the temperature further raised, there can be a pure $e^{i2 heta}$ quasi-long range ordered phase before the fully disordered phase. The phase diagram is different from the previous prediction of a nematic superconductor with an additional nematic power-law phase here. We believe that domain wall proliferation and the interplay of charge-4e and nematic order are responsible for this nematic power-law phase. Nevertheless, vortex proliferation is still responsible for the formation of the pure charge-4e phase and the direct transition to a fully disordered phase. |
Tuesday, March 7, 2023 5:36PM - 5:48PM |
K29.00014: Symmetries, Band Flattening and Fractional Chern Insulators Ady L Stern, Raquel Queiroz, Yarden Sheffer Since the discovery of magic-angle twisted bilayer graphene, flat bands in Dirac materials have become a prominent platform for realizing strong correlation effects in electronic systems. Here we show that the symmetry group protecting the Dirac cone in such materials determines whether a Dirac band may be flattened by the tuning of a small number of parameters. We devise a criterion that, given a symmetry group, allows for the calculation of the number of parameters required to make the Dirac velocity vanish. This criterion is employed to study band flattening in twisted bilayer graphene and in surface states of 3D topological insulators. Following this discussion, we identify the symmetries under which the vanishing of the Dirac velocity implies the emergence of perfectly-flat bands. Finally, we draw conclusions from our analysis regarding the formation of fractional Chern insulator states. |
Tuesday, March 7, 2023 5:48PM - 6:00PM |
K29.00015: Abstract Withdrawn |
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