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 C43: Correlated Electrons in 2DLive
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Sponsoring Units: DCMP Chair: Rabindranath Bag, Duke University |
Monday, March 15, 2021 3:00PM - 3:12PM Live |
C43.00001: Interplay between Electron Pairing and Nonlinear Hall Effect in LaAlO3/SrTiO3 nanostructures Aditi Nethwewala, Hyungwoo Lee, Jianan Li, Megan K Briggeman, Yun-Yi Pai, Jungwoo Lee, Chang-Beom Eom, Patrick R Irvin, Jeremy Levy The widely reported nonlinear Hall effect in LaAlO3/SrTiO3 heterostructures has been attributed to multiband carrier transport in SrTiO3, combined with metamagnetic transitions of unspecified origin. Here, we report simultaneous longitudinal and Hall measurements in quasi-1D cross-shaped electron waveguides (“nanocrosses”) created at the LaAlO3/SrTiO3 interface using conductive atomic force microscope lithography. The nonlinear Hall response is directly correlated with the transition of electrons from the non-superconducting paired state to the unpaired state at the LaAlO3/SrTiO3 interface. These transport measurements strengthen the connection between previously reported metamagnetic effects in gated 2D LaAlO3/SrTiO3 heterostructures and the electron pairing-depairing transition in conductive nanostructures. |
Monday, March 15, 2021 3:12PM - 3:24PM Live |
C43.00002: Non-Fermi Liquids in Conducting 2D Networks Jongjun Lee, Masaki Oshikawa, Gil Young Cho We explore the physics of novel fermion liquids emerging from conducting networks, where 1D metallic wires form a periodic 2D superstructure. Such structure naturally appears in marginally-twisted bilayer graphenes, moire transition metal dichalcogenides, and also in some charge-density wave materials. For these network systems, we theoretically show that a remarkably wide variety of new non-Fermi liquids emerge and that these non-Fermi liquids can be classified by the characteristics of the junctions in networks. Using this, we calculate the electric conductivity of the non-Fermi liquids as a function of temperature, which show markedly different scaling behaviors than a regular 2D Fermi liquid. |
Monday, March 15, 2021 3:24PM - 3:36PM Live |
C43.00003: Manipulation of electron-phonon energy transfer pathways in 2D transition metal dichalcogenides through ultrafast excitation Christian Gentry, Emma Cating-Subramian, Sinead Annie Ryan, Wenjing You, Xun Shi, Henry C Kapteyn, Margaret Murnane The complex phase landscape of quantum materials provides tremendous opportunity for design, manipulation, and coherent control of material properties using light. Understanding that complexity also poses a significant challenge, and multiple techniques are needed to map and exploit the rich phase space of strongly correlated materials. For example, using ultrafast electron calorimetry via time- and angle-resolved photoemission (ARPES), a bi-directional energy transfer between strongly-correlated electron and phonon modes in a material has been observed for the first time - in this case a charge density wave (CDW) material 1T-TaSe2. |
Monday, March 15, 2021 3:36PM - 3:48PM Live |
C43.00004: Energy relaxation in a low-density nonequilibrium 2D hole gas at the quantum hall plateau-plateau transition Dmitrii Kruglov, Elina Klysheva, Andrei Kogan, Chieh-Wen Liu, Xuan Gao, Loren Pfeiffer, Ken W. West We have measured the derivative S = dRxy/dB of the transverse resistance Rxy vs magnetic field B at the ν=3 -> ν=2 (B=0.45 T) quantum Hall plateau-plateau transition (PPT) , as function of the sample temperature T and dissipated Joule’s power P in a low-density, p-doped GaAs/AlGaAs quantum well with a high interaction parameter rs ~ 23 (nh= 2.9 x 1010 /cm-2, hole mobility μ = 2.4 x 105 cm2/Vs). We present P-T curves constructed by matching P and T values at a given S, and compare these to a set of similar curves obtained for the sample resistance R at B=0. At low temperatures, the P-T data in the magnetic field and at B=0 diverge suggesting that the thermal coupling between the holes and the lattice increases in the magnetic field and makes the holes effectively cooler at a given P. We also find that the thermal coupling in the magnetic field shows a weaker temperature dependence than at B=0. We compare these findings to an earlier work on a system with a lower rs=2.17 [1] and discuss possible nonlinear effects near the PPT under conditions of electric current flow. [1] Edmond Chow, H. P. Wei, S. M. Girvin, and M. Shayegan. Phys. Rev. Lett., 1996. Vol. 77(6), pp 1143-1146. |
Monday, March 15, 2021 3:48PM - 4:00PM Live |
C43.00005: Electrically controlled two-dimensional electron-hole fluids Yongxin Zeng, Allan MacDonald Recent advances in experimental techniques have opened up the possibility of electrical control of electron-hole bilayer systems. In this talk I will discuss the electronic properties of a dual-gated electron-hole bilayer in which the two layers are separated by a perfectly opaque tunnel barrier. Combining an electrostatic and thermodynamic analysis [1] with mean-field theory estimates of interacting system chemical potentials, we explain the dependence of the electron and hole densities on the two gate voltages. We find a finite area in gate voltage parameter space over which electron and hole densities are equal and the electron-hole pair density depends only on the bias voltage which acts like a chemical potential for excitons. I will briefly discuss the transport properties of exciton circuits formed in systems with two or more exciton reservoirs, and a recent related experimental study [2] of electrically controlled bilayers that realizes a non-equilibrium steady-state instead of a quasi-equilibrium. |
Monday, March 15, 2021 4:00PM - 4:12PM Live |
C43.00006: Renormalized analytic solution for the enstrophy cascade in two-dimensional quantum turbulence-3 Andrew Forrester, Han-Ching Chu, Gary Williams The forward enstrophy cascade in two-dimensional quantum turbulence in a superfluid film connected to a thermal bath is investigated using a Fokker-Planck equation based on Kosterlitz-Thouless renormalization. The steady-state cascade is formed by injecting vortex pairs of large initial separation at a constant rate. They diffuse with a constant flux to smaller scales, finally annihilating when reaching the core size. The energy spectrum varies as k-3, similar to the spectrum known for 2D classical-fluid enstrophy cascades. The dynamics of the cascade can also be studied, and for the case of a sharply peaked initial vortex-pair distribution, it takes about four eddy turnover times for the system to evolve to the decaying k-3 cascade, in agreement with recent computer simulations. These insights into the nature of the cascade also allow a better understanding of the phase-ordering process of temperature-quenched 2D superfluids, where the decay of the vorticity is found to proceed via the turbulent cascade. This connection with turbulence may be a fundamental characteristic of phase-ordering in general. |
Monday, March 15, 2021 4:12PM - 4:24PM Not Participating |
C43.00007: Hilbert space fragmentation and hydrodynamics in two-dimensional systems Julius Lehmann, Tibor Rakovszky, Pablo Sala de Torres-Solanot, Frank Pollmann Higher-moment conservation in lattice systems can lead to Hilbert space fragmentation and anomalous transport. While many physical insights can be already drawn from one-dimensional systems, we uncover a richer structure in the two-dimensional case. We find that different components of the quadrupole moment can be conserved and, in the weakly fragmented regime, lead to potentially different hydrodynamic descriptions which in all cases results in subdiffusion. To validate these concepts, we numerically investigate the stochastic evolution of blocked cellular automata with higher-moment conservation. |
Monday, March 15, 2021 4:24PM - 4:36PM Live |
C43.00008: Anomalous density fluctuations in a random t-J model Darshan Joshi, Subir Sachdev A previous work [1] found a deconfined critical point at nonzero doping in a t -J model with all-to-all and random hopping and spin exchange and argued for its relevance to the phenomenology of the cuprates. We extend this model to include all-to-all and random density-density interactions of mean-square strength K. In a fixed realization of the disorder, and for specific values of the hopping, exchange, and density interactions, the model is supersymmetric, but we find no supersymmetry after independent averages over the interactions. Using the previously developed renormalization group analysis, we find a new fixed point at nonzero K. However, this fixed point is unstable toward the previously found fixed point at K = 0 in our perturbative analysis. We compute the exponent characterizing local density fluctuations at both fixed points: This exponent determines the spectrum of electron energy-loss spectroscopy. |
Monday, March 15, 2021 4:36PM - 4:48PM Live |
C43.00009: Nematic fluctuations in the Hubbard model Tianyi Liu, Edwin Huang, Brian John Moritz, Thomas Devereaux An electron nematic is an electronic phase with translation symmetry, but broken rotational symmetry. Signatures of nematic fluctuations have been observed in strongly correlated materials such as cuprates, iron pnictide, and iron chalcogenide superconductors, and may be related with other sorts of broken symmetries such as charge or spin density waves. Here we report calculations of the nematic susceptibilities from determinant quantum Monte Carlo (DQMC) simulations of the Hubbard model, for various model parameters, doping levels, and temperatures. We draw possible connections between these susceptibilities to other phenomena observed in the Hubbard model. |
Monday, March 15, 2021 4:48PM - 5:00PM Live |
C43.00010: Luttinger Breaking Fermi-surface in the Repulsive Fermi-Hubbard Model Ian Osborne, Nandini Trivedi, Thereza Paiva One of the fundamental questions about the high temperature cuprate superconductors is the size of the Fermi surface (FS) underlying the superconducting state. By analyzing the single particle spectral function for the Fermi Hubbard model as a function of repulsion U and chemical potential μ, we find that the Fermi surface in the normal state undergoes a transition from a large Fermi surface matching the Luttinger volume as expected in a Fermi liquid, to a Fermi surface that encloses fewer electrons that we dub the "Luttinger Breaking" (LB) phase, as the Mott insulator is approached. This transition into a non-Fermi liquid phase that violates the Luttinger count occurs at a critical density in the absence of any other broken symmetry. We obtain the Fermi surface contour from the spectral weight Ak(ω=0) and from an analysis of the singularities of the Green's function Re[Gk(E=0)], calculated using determinantal quantum Monte Carlo and analytic continuation methods. We discuss our numerical results in connection with experiments on Hall measurements, scanning tunneling spectroscopy, and, angle resolved photoemission spectroscopy. |
Monday, March 15, 2021 5:00PM - 5:12PM Live |
C43.00011: Dynamics of a two-dimensional quantum spin-orbital liquid: spectroscopic signatures of fermionic magnons Willian Natori, Johannes Knolle Quantum spin liquids research has gained increased attention due to the synthesis of novel compounds that possibly host these phases. In some of these candidates, the local Hilbert spaces display additional orbital degrees of freedom, which opens the possibility of new routes for fractionaled excitations. In this talk, we discuss the dynamical correlations of quantum spin-orbital liquid phases of an SU(2)-symmetric Kitaev honeycomb lattice model [1]. We show that its spin dynamics is exactly the density-density correlation function of S=1 fermionic magnons, which could be probed in resonant inelastic x-ray scattering experiments. This prediction is contrasted to the expected signatures in inelastic scattering experiments, which displays a mixed response of fermionic magnons as well as spin-orbital excitations. The latter has a bandwidth of broad excitations and a vison gap that is three times larger than that of the spin-1/2 Kitaev model. The relevance of our results to real materials and directions for future research are also discussed. |
Monday, March 15, 2021 5:12PM - 5:24PM Live |
C43.00012: Temperature-Dependent Magnetization, Raman Scattering, and X-Ray Diffraction Study of Phase Transitions in Layered Multiferroic CuCrP2S6 Michael Susner, Rahul Rao, Bing Lv, Benjamin S Conner, wenhao liu, Anthony Pelton, McLeod V Michael, Benji Maruyama Functional van der Waals layered materials exhibit interesting phenomena such as magnetism and ferroelectricity and have been proposed for use in next-generation nanoscale devices. Metal thiophosphates are an interesting class of these materials that contain a common structural framework where altering the cation can induce different types of ferroic ordering, including ferroelectricity and magnetism. The compound CuCrP2S6 is a promising 2D material that evinces multiferroic behavior where the Cu+ and Cr+3 cations are responsible for antiferroelectric (AFE) and antiferromagnetic ordering, respectively, which are predicted to couple. Here, we use magnetization, X-ray diffraction, and Raman spectroscopy to map out these phase transitions. The AFE phase transition is complex and shows a gradual transition to complete antipolar order with an intermediate quasi-antipolar step. X-ray diffraction studies reveal evidence for negative thermal expansion which we argue is tied to magnetic frustration. This is accompanied by a drastic reduction in rotational and translational mode frequencies of the anion groups in CuCrP2S6. Our temperature-dependent structural data provides an important reference for subsequent research into this promising 2D multiferroic material. |
Monday, March 15, 2021 5:24PM - 5:36PM Live |
C43.00013: Machine Learning Enable the Large Scale Kinetic Monte Carlo for Falicov-Kimball Model Sheng Zhang, Puhan Zhang, Gia-wei Chern The Falicov-Kimball (FK) model was initially introduced as a statistical model for metal-insulator transition in correlated electron systems. It can be exactly solved by combining the classical Monte Carlo method for the lattice gas and exact diagonalization (ED) for the itinerant electrons. However, direct ED calculation, which is required in each time-step of dynamical simulations of the FK model, is very time-consuming. Here we apply the modern machine learning (ML) technique to enable the first-ever large-scale kinetic Monte Carlo (kMC) simulations of FK model. Using our neural-network model on a system of unprecedented 10^5 lattice sites, we uncover an intriguing hidden sub-lattice symmetry breaking in the phase separation dynamics of FK model. |
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