Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session E44: Superconducting and Superfluid InstabilitiesLive
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Sponsoring Units: DCMP Chair: Andriy Nevidomskyy, Rice Univ |
Tuesday, March 16, 2021 8:00AM - 8:12AM Live |
E44.00001: Modeling unconventional superconductivity at the crossover between strong and weak electronic interactions Morten Holm Christensen, Xiaoyu Wang, Yoni Schattner, Erez Berg, Rafael Fernandes The interplay between superconductivity and magnetism in correlated systems is an outstanding question in condensed matter physics. It has been recently shown that the two-band spin-fermion model, in which electrons interact with pre-existing magnetic fluctuations, can be simulated by Quantum Monte Carlo (QMC) without the fermionic sign-problem. Here we go beyond this approach and present sign-problem-free QMC results of a two-band microscopic model in which both superconductivity and magnetism arise from the very same inter-band repulsion, without pre-existing bosons mediating the electronic interactions. Our simulations reveal the interplay between a host of different phenomena as the interaction strength is increased. A wide magnetic dome appears at moderate values of the interaction, whereas a narrow superconducting dome emerges around the magnetic quantum critical point located on the less strongly correlated side of the phase diagram. Interestingly, a metal-insulator transition is nearly coincident with this magnetic phase boundary, and is manifested by a change in the magnetic dynamics from overdamped to propagating. The emergence of superconductivity only in the former region provides important clues about the nature of the pairing glue in unconventional superconductors. |
Tuesday, March 16, 2021 8:12AM - 8:24AM Live |
E44.00002: Charge Density Wave and Superconductivity in the Disordered Holstein Model Bo Xiao, Natanael Costa, Ehsan Khatami, George Batrouni, Richard Theodore Scalettar The interplay between electron-electron correlations and disorder has been a central theme of condensed matter physics over the last several |
Tuesday, March 16, 2021 8:24AM - 8:36AM Live |
E44.00003: Superconducting instabilities in spinful SYK models Etienne Lantagne-Hurtubise, Vedangi Pathak, Sharmistha Sahoo, Marcel Franz In this talk I will introduce a solvable toy model for correlated superconductivity in 0+1 dimensions: a spinful generalization of the Sachdev-Ye-Kitaev model with time-reversal invariant interactions. Its phase diagram includes a correlated superconducting phase that emerges out of a gapless non-Fermi liquid through the spontaneous breaking of the system's global U(1) symmetry. I will then discuss lattice constructions of higher-dimensional superconducting phases based on such spinful SYK models |
Tuesday, March 16, 2021 8:36AM - 8:48AM Live |
E44.00004: Inducing and controlling superconductivity in Hubbard honeycomb model using an electromagnetic drive Umesh Kumar, Shi-Zeng Lin The recent successful experimental observation of quantum anomalous Hall effect in graphene under laser irradiation demonstrates the feasibility of controlling single-particle band structure by lasers. Here we study superconductivity in a Hubbard honeycomb model in the presence of an electromagnetic drive. We start with the Hubbard honeycomb model in the presence of an electromagnetic field drive; both, (a) circularly and (b) linearly polarized light, and map it onto a Floquet t-J model. We study the Floquet t-J model within the mean-field theory in the singlet pairing channel and explore superconductivity for small doping in the system using the Bogoliubov-de Gennes approach. We uncover several superconducting phases, which break lattice or time-reversal symmetries. We show that the unconventional chiral SC order parameter (d+id) can be driven to a nematic SC order parameter (s+d) in the presence of a circularly polarized light. We further show that the three-fold nematic degeneracy can be lifted using linearly polarized light. Our work, therefore, provides a generic framework for inducing and controlling SC in the Hubbard honeycomb model, with possible application to graphene and other two-dimensional materials. |
Tuesday, March 16, 2021 8:48AM - 9:00AM Live |
E44.00005: Competing nodal d-wave superconductivity and antiferromagnetism: a Quantum Monte Carlo study Xiao Yan Xu, Tarun Grover Unconventional superconductors such as cuprates often host competing nodal superconductivity and antiferromagnetism. These systems are typically modeled as a repulsive Hubbard model whose unbiased simulation suffers from the fermion sign-problem at any non-zero doping. Here we will exploit the fact that neither of these phases, the nodal d-wave superconductor or the antiferromagnet, require any doping for their existence, and construct a sign-problem-free repulsive Hubbard model with an additional bosonic field which hosts both of these phases. Using Quantum Monte Carlo (QMC) simulations, supplemented with mean-field theory and continuum field-theory arguments, we find that it hosts three distinct phases: a nodal d-wave phase, an antiferromagnet, and an intervening phase which hosts coexisting antiferromagnetism and nodeless d-wave superconductivity. The transition from the coexisting phase to the antiferromagnet is described by the 2+1-D XY universality class, while the one from the coexisting phase to the nodal d-wave phase is described by the chiral Gross-Neveu-Heisenberg theory. |
Tuesday, March 16, 2021 9:00AM - 9:12AM Live |
E44.00006: Photoinduced Enhancement of Superconductivity in the Plaquette Hubbard Model Yuxi Zhang, Rubem Mondaini, Richard Theodore Scalettar Real-time dynamics techniques have been proven useful in understanding strongly correlated systems both theoretically and experimentally. By employing unbiased time-resolved exact diagonalization, we performed numerical simulations to study pump dynamics in the two-dimensional plaquette Hubbard model, where t and t' are used to represent hopping integrals within and between plaquettes. In the intermediate coupling regime, an enhancement of d-wave superconductivity is observed and examined via comparison with eigenstates of the Hamiltonian. Our work provides further understanding of superconductivity in the Hubbard model and offers an promising approach for experimentally engineering emergent states out of equilibrium. |
Tuesday, March 16, 2021 9:12AM - 9:24AM Live |
E44.00007: Dynamical Order and Superconductivity in a Frustrated Many-Body System Joseph Tindall, Frank Schlawin, Michele Buzzi, Daniele Nicoletti, Hongmin Gao, Jonathan Coulthard, Andrea Cavalleri, Michael Sentef, Dieter Jaksch In triangular lattice structures, spatial anisotropy and frustration can lead to rich equilibrium phase diagrams with regions containing complex, highly entangled states of matter. We study the driven two-rung triangular Hubbard model and evolve these states out of equilibrium, observing how the interplay between the driving and the initial state unexpectedly shuts down the particle-hole excitation pathway. This restriction, which symmetry arguments fail to predict, dictates the transient dynamics of the system, causing the available particle-hole degrees of freedom to manifest uniform long-range order. Our results have implications for a recent experiment on photoinduced superconductivity in κ−(BEDT−TTF)2Cu[N(CN)2]Br molecules. |
Tuesday, March 16, 2021 9:24AM - 9:36AM Live |
E44.00008: Dynamics of stripe pattern formation in high-Tc superconductors following a quench Minhui Zhu, Denitsa Baykusheva, Peter Abbamonte, Matteo Mitrano, Nigel Goldenfeld Recent experiments using ultrafast time-resolved X-ray scattering have succeeded in probing the charge order dynamics in high temperature superconductors, following a sudden quench of the system. Here, we investigate the relaxation dynamics of the quench process of stripe ordering from disordered states, using the Swift-Hohenberg equation as a phenomelogical model forthe collective modes of charge density waves. We calculate the relaxation rate of the structure factor shortly after the quench perturbatively, and extract the diffusive properties by fitting the relaxation rate in 2D momentum space. We numerically simulate the quench process in a 2D system, representing a copper-oxygen plane, and through a direct measurement, we determine the transport properties and compare with experimental results. |
Tuesday, March 16, 2021 9:36AM - 9:48AM Live |
E44.00009: Non Fermi liquid scattering and pseudogap: spectral features from a meanfield with partial incoherence of lower dimension Xinlei Yue, Xiang Li, Wei Ku Non-fermi liquid behavior and pseudogap formation are examples of exotic spectral features observed in hole-doped cuprates and some other strongly correlated materials. Considering the necessity of coherence for gap formation, and incoherence for filling the gap with states, these characteristic features are often believed to originate from strong fluctuation in the critical region or vicinity of a long-range order. Here we propose that these features can also come from coupling to an unconventional ''Bose metal'' meanfield, which contains perfect coherence and partial phase incoherence of lower dimension. Such a meanfield can exist in the Bose metal phase and thus can act in a much wider region of the phase diagram beyond just the critical region. |
Tuesday, March 16, 2021 9:48AM - 10:00AM Live |
E44.00010: A study of momentum dependent electron-phonon-couplings in Ab-initio Cuprate Hamiltonians Nahom Yirga, David Campbell We use the functional renormalization group (fRG) to study the impact of strong electron-phonon couplings on effective Cuprate Hamiltonians with up to three bands. In the single band case, we reproduce the transition from an antiferromagnet (AF) to a charge density wave (CDW) seen in the Hubbard-Holstein model. For electron-phonon couplings without momentum dependence, we show the transition from a charge density wave to a s-superconductivity as a function of the phonon frequency. We then look at changes to the phase diagram due to the momentum dependent A1g and B1g phonon modes of the Cuprate systems. The two phonon modes enhance extended s-wave and dx2-y2 superconducting fluctuations along the AF-CDW transition line. The modes also shift the transition into the CDW phase as we increase the electron-phonon coupling. The effects of the A1g mode are unchanged in the two band model while B1g modes with frequency less than the separation between dz2 and dx2-y2 orbitals appear to drive momentum dependent charge orders. Finally, we consider the role of the frequency of the phonon modes and doping in the three band case. |
Tuesday, March 16, 2021 10:00AM - 10:12AM Live |
E44.00011: Three-dimensional electron-hole superfluidity in a superlattice close to room temperature Sara Conti, Matthias Van der Donck, David Neilson, Andrea Perali, Alex Hamilton, Bart Partoens, Francois Peeters Bound pairs of electrons and holes in semiconductors may condense into a superfluid. The electron-hole coupling is predicted to be much stronger than in conventional superconductors when the electrons and holes are confined in separated layers. |
Tuesday, March 16, 2021 10:12AM - 10:24AM Live |
E44.00012: Dimensional crossover and phase transitions in coupled chains: DMRG results Per Bollmark, Adrian Kantian Quasi-one-dimensional (Q1D) systems are often studied across various areas of condensed matter and ultracold atomic lattice-gas physics and are often marked by dimensional crossover (DC) as the coupling between one-dimensional systems is increased or temperature decreased. Understanding these crossovers can be challenging due to the very different elementary excitations of 1D systems compared to higher-dimensional ones. In the present work, we combine numerical matrix product state (MPS) methods with mean-field (MF) theory to study paradigmatic cases of DC in systems of hard- and soft-core lattice bosons, with relevance to both condensed matter physics and ultracold atomic gases. We show that the superfluid-to-insulator transition is a first order one, as opposed to the isotropic cases and calculate transition temperatures for the superfluid states, finding excellent agreement with analytical theory while still functioning well where the current analytical framework does not apply. We further confirm the reliability of our approach by comparison to exact Quantum Monte Carlo calculations for the full 3D arrays. |
Tuesday, March 16, 2021 10:24AM - 10:36AM Live |
E44.00013: Manipulating intertwined orders in solids with quantum light Jiajun Li, Martin Eckstein Intertwined orders exist ubiquitously in strongly correlated electronic systems and lead to intriguing phenomena in quantum materials. In this paper, we explore the unique opportunity of manipulating intertwined orders through entangling electronic states with quantum light. Using a quantum Floquet formalism to study the cavity-mediated interaction, we show the vacuum fluctuations effectively enhance the charge-density-wave correlation, giving rise to a phase with entangled electronic order and photon coherence, with putative superradiant behaviors in the thermodynamic limit. Furthermore, upon injecting even one single photon in the cavity, different orders, including s–wave and η–paired superconductivity, can be selectively enhanced. Our study suggests a new and generalisable pathway to control intertwined orders and create light-matter entanglement in quantum materials. The mechanism and methodology can be readily generalised to more complicated scenarios. |
Tuesday, March 16, 2021 10:36AM - 10:48AM Live |
E44.00014: Critical Anomalous Metal Near Superconductivity in a Random Hubbard Model Chenyuan Li, Darshan Joshi, Subir Sachdev We study the quantum phase transition between a superconductor and a metal within a half-filled Hubbard model of electrons with random and all-to-all hopping and exchange. A perturbative renormalization group analysis yields a deconfined critical point at U=0 with fractionalized excitations. We obtain exponents for the electron and spin correlators to all orders in perturbation theory. These are same as those found in a random t-J model at finite doping [1] and exhibit a SYK-like behavior. We also calculate the exponents for the superconductor order parameter and density to one-loop order. A large M analysis for models with SU(M) spin symmetry provides additional evidence for the critical behavior. Investigation of the background conductivity at zero temperature indicates the existence of critical anomalous metal phase near superconductivity in this model. |
Tuesday, March 16, 2021 10:48AM - 11:00AM Live |
E44.00015: Optimized pairing from repulsive interactions in Fermi-Hubbard ladders and its static and dynamic signatures Thomas Koehler, Adrian Kantian Experiments on Fermi-Hubbard models, implemented via lattice-confined ultra-cold gases, are moving towards temperatures where their charge gap and possibly their spin gap can be resolved. It is thus important to obtain accurate quantitative theory for those systems in order to optimize the chance of observing any possible unconventional pairing from repulsive interactions at the given temperatures of the ongoing experiments. |
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