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 Q61: Precision Many Body Physics III: Novel Quantum StatesFocus
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Sponsoring Units: DCOMP Chair: Hansveer Singh, University of Massachusetts, Amherst Room: Room 418 |
Wednesday, March 8, 2023 3:00PM - 3:36PM |
Q61.00001: Flat bands and band touching in hyperbolic lattices Invited Speaker: Joseph Maciejko Recent years have witnessed much interest in condensed matter systems that exhibit flat bands, i.e., energy bands of a tight-binding Hamiltonian that are independent of the crystal momentum. Since the ratio of interaction potential energy to kinetic energy diverges for a dispersionless band, flat-band systems are fertile grounds to engineer exotic many-body states, including ferromagnetism, superconductivity, Wigner crystallization, and the fractional quantum Hall effect. Hopping models on geometrically frustrated lattices, such as the kagome and dice lattices, exhibit perfectly flat energy bands that result from eigenstates localized along contractible and/or noncontractible loops in real space. The key properties of those flat bands, such as their degeneracy and possible touchings with other dispersive bands, follow from an intriguing interplay between real-space topology and momentum-space band theory. In this talk, I will discuss how to generalize this paradigm to frustrated hyperbolic lattices, such as those realized in recent circuit quantum electrodynamics experiments, which may open new avenues for many-body physics with synthetic quantum systems. I will explain how hyperbolic flat-band characteristics can similarly be understood by combining real-space topology arguments with the recently developed hyperbolic band theory. |
Wednesday, March 8, 2023 3:36PM - 3:48PM |
Q61.00002: Supercell construction and non-Abelian Bloch states in hyperbolic lattices Patrick M Lenggenhager, Joseph Maciejko, Tomas Bzdusek Hyperbolic {p,q}-lattices are tessellations of the sheet of constant negative curvature such that q copies of regular p-sided polygons meet at each vertex. The spectra of such lattices were recently characterized with hyperbolic band theory. Here, given a concrete hyperbolic lattice, one first constructs the hyperbolic translation group (HTG). The fundamental domain of the HTG defines a hyperbolic unit cell, and its Abelian representations span a four- (or higher-) dimensional Brillouin zone of Abelian Bloch states. However, this approach fails to capture non-Abelian Bloch states which transform in higher-dimensional representations. |
Wednesday, March 8, 2023 3:48PM - 4:00PM |
Q61.00003: Optical Conductivity of Low Density and Dirac Systems: Exact Perturbative vs Dynamical Mean Field Results Anqi Mu, Zhiyuan Sun, Andrew Millis We compute the electron self energy and the optical conductivity of both Hubbard models in the limit of low density and Dirac systems with the chemical potential near the Dirac point using both exact perturbative and the dynamical mean field approximation when the interaction is weak. The strong momentum dependence of the self energy implies that the dynamical mean field approximation is a fundamentally inaccurate representation of the low frequency electron scattering dynamics; furthermore, vertex corrections, neglected in DMFT-based calculations, change the low frequency conductivity qualitatively, but in different ways in the low density cubic lattice and Dirac systems. |
Wednesday, March 8, 2023 4:00PM - 4:12PM |
Q61.00004: Spectral properties of $CuO$ chains across a Hubbard to charge-transfer insulator crossover Samuel J Milner, Adrian E Feiguin We carry out extensive numerical calculations of the photoemission spectra, optical conductivity and resonant inelastic X-ray scattering (RIXS) Cu $L$ edge spectrum of a generalized two band model for $CuO$ chains by means of the time dependent density matrix renormalization group method. By varying the Hamiltonian parameters, we study the crossover from Hubbard to charge-insulator and characterize the spectral signatures of the two regimes. We compare our results with experiments on the single chain oxide Sr$_2$CuO$_3$. |
Wednesday, March 8, 2023 4:12PM - 4:24PM |
Q61.00005: Superconducting transition temperature of the Bose one-component plasma Nikolay Prokof'ev, Boris Svistunov, Barbara Capogrosso-Sansone, Chao Zhang, Massimo Boninsegni We present results of first principle numerical simulations of the Bose one-component plasma, i.e., a Bose gas with pairwise Coulomb interactions among particles and a uniform neutralizing background. We compute the superconducting transition temperature for a wide range of densities, in two and three dimensions, for both continuous and lattice versions of the model. Our results are of direct relevance to quantitative studies of bipolaron mechanisms of (high-temperature) superconductivity and indicate that the effect of the Coulomb interactions on Tc proves remarkably modest even at large rs, when the system is close to the Wigner crystal phase. |
Wednesday, March 8, 2023 4:24PM - 4:36PM |
Q61.00006: Exploring the Fermi polaron problem with canonical-ensemble auxiliary-field quantum Monte Carlo Shasta Ramachandran, Scott Jensen, Yoram Alhassid The behavior of an impurity that interacts strongly with a Fermi sea is of fundamental importance in quantum many-body physics. This system has been realized experimentally in ultra-cold atomic Fermi gases with tunable attractive short-range interactions. In the so-called unitary limit of infinite scattering length, there is a crossover from a dressed quasiparticle, known as the Fermi polaron, at low temperatures to a classical Boltzmann gas at high temperatures. As a function of the interaction strength at zero temperature, there is a transition from a Fermi polaron to a dressed molecule. We explore the thermodynamics of the Fermi polaron problem using canonical-ensemble auxiliary-field quantum Monte Carlo methods by projecting on an N-particle Fermi sea of spin-up particles and on one spin-down particle. Our calculations are carried out on discrete lattices and extrapolated to the continuum limit. |
Wednesday, March 8, 2023 4:36PM - 4:48PM |
Q61.00007: Decay Rate of the Tkachenko mode Yi-Hsien Du, Sergej Moroz, Dung X Nguyen, Dam T Son We construct a low-energy effective field theory of the Tkachenko mode in a rotating two-dimensional superfluid. This theory has an exotic symmetry which is a nonlinear version of the dipole symmetry. Using the symmetry we determine the energy dependence of the decay rate of the Tkachenko mode in the long-wavelength limit. |
Wednesday, March 8, 2023 4:48PM - 5:00PM |
Q61.00008: Coherence in Strongly Coupled rf SQUID metamaterials Jingnan Cai, Steven M Anlage The radio frequency Superconducting Quantum Interference Device (rf SQUID) has been established as a viable building block for microwave frequency metamaterials [1,2]. The nonlinearity and nonlocal coupling of rf SQUID metamaterials endow them with interesting dynamical properties, such as chaos and chimera states, both of which have been studied extensively by theorists in the context of rf SQUID metamaterials [3,4,5,6]. In this work, laser scanning microscopy [7] with single SQUID resolution is employed to study collective states of the nonlinear metamaterial with strong inductive and capacitive couplings. Chimeras and complex modes are expected to emerge from a strongly interacting and highly nonlinear system. These nontrivial behaviors demonstrated the potential of the rf SQUID metamaterial as a platform to study many-body physics. |
Wednesday, March 8, 2023 5:00PM - 5:12PM |
Q61.00009: Many-body Approach for XAS and XMCD Applied to Ferrites Felix Sorgenfrei, Patrik Thunstrom, Olle Eriksson, Mebarek Alouani X-ray absorption spectroscopy is an important tool to extract element-specific information about the electronic structure, magnetism and in particular electronic correlation effects. |
Wednesday, March 8, 2023 5:12PM - 5:24PM |
Q61.00010: Investigating Zhang-Rice state across magnetic transition in Mott Insulator MnO Subhasish Mandal, Asish K Kundu Using the combination of ab initio embedded dynamical mean-field theory (eDMFT) and angle-resolved-photoemission-spectroscopy (ARPES), we study the effect of long-range magnetic ordering on the spectral properties of the Mott insulating MnO (001). We find that the most significant changes develop in the momentum-resolved spectral functions, which sharpen into quite well-defined bands in the antiferromagnetic (AFM) phase. The strongest change appears at the Zhang-Rice bound state, which strengthens in the AFM phase for the minority spin component, due to stronger fluctuations. A similar hybridized bound state also emerges in the DFT single-particle description of the AFM phase but gets much stronger and acquires well-defined energy in the eDMFT description. |
Wednesday, March 8, 2023 5:24PM - 5:36PM |
Q61.00011: Electronic structure and optical response of rare-earth semiconductors obtained by semi-local exchange and dynamical mean-field theory Anna Galler Rare-earth semiconductors such as the rare-earth mononitrides LnN (with Ln=rare-earth) or fluorosulfides LnSF are technologically promising materials with applications ranging from spintronics to optics. Their electronic structure is very challenging for theory, since wide conduction and valence bands coexist with Mott localized rare-earth 4f states. Here, I present a computational method combining a dynamical mean-field theory approach to strong local correlations with a perturbative application of the semi-local modified Becke-Johnson exchange potential to correct the semiconducting gap. In this approach, the on-site Coulomb interaction in the 4f shell is evaluated from first principles. I apply this method to calculate the electronic structure and optical response of the rare-earth mononitrides LnN and the rare-earth fluorosulfides LnSF, which are prospective spintronics and pigment materials, respectively. I show that the employed method can reliably predict their electronic spectral function as well as the evolution of the optical absorption edge in the investigated compounds. |
Wednesday, March 8, 2023 5:36PM - 5:48PM |
Q61.00012: Construction and Solutions of Quadratic Effective Hamiltonians for Magnetic Impurities Xindong Wang We demonstrate that the chiral symmytry breaking quadratic effective Hamiltonians for magnetic impurities embbeded in a non-interacting fermionic reservoir can be constructued in a self-consistent manner. The solutions of the quadratic effective Hamiltnian corresponds to the ground state and single fermion excitations. Results for Anderson Impurity model and more realistic magnetic inpurities are presented. |
Wednesday, March 8, 2023 5:48PM - 6:00PM Author not Attending |
Q61.00013: Applications of the Heisenberg-Euler Weak-Field Expansion Simulator Baris Oelmez, Andreas Lindner, Hartmut Ruhl With the advent of high power lasers, the experimental detection of dynamic quantum vacuum effects comes within reach giving reason to the need of advanced numerical simulations. To understand quantum electrodynamics (QED) the numerical approach is inevitable. While most of the numerical solvers have problems in the effective QED regime, our solver is capable of simulating different scenarios in the Heisenberg-Euler regime in the weak-field limit in multiple dimensions and for a variety of scenarios reliably. In the talk multiple setups are introduced and discussed by simulating colliding laser pulses. In particular, the phenomenon of light-by-light focusing is addressed and simulated in two dimensions and in addition setups of flipping scenarios are covered. |
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