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 K30: Strongly Correlated Systems, Including Quantum Fluids and Solids VIII |
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Sponsoring Units: DCMP Chair: Yang Ge, University of Cincinnati Room: Room 222/223 |
Tuesday, March 7, 2023 3:00PM - 3:12PM |
K30.00001: CW NMR Studies of Quasi-1D 3He Below the Fermi Temperature Johnny L Adams, Marc L lewkowitz, Chao Huan, Naoto Masuhara, Neil S Sullivan, Donald Candela Theorists have predicted new quantum states can emerge for quantum fluids (3He, 4He, H2, HD) constrained to nanoscale dimensions where the thermal de Broglie wavelength and/or Fermi length are comparable to the channel size [1, 2]. In this experimental study, CW NMR techniques have been used to investigate the dynamics of quasi-1D 3He at low temperatures where pulsed NMR techniques cannot be used because of excessive RF heating. Specifically the nuclear spin relaxation times were obtained at temperatures down to 15 mK for 3He constrained to the interior of 4He-plated MCM-41, allowing for a more complete determination of the dynamics. |
Tuesday, March 7, 2023 3:12PM - 3:24PM |
K30.00002: Hydrodynamic stability of superfluids and the Landau criteria Eric Mefford The Landau criteria states that superfluidity can exist in nature because, up to some critical velocity, the superfluid may flow relative to a system at rest without creating dissipative excitations. This criteria governs the microscopics of superfluids but, like any other fluid, there also exists a hydrodynamic formulation describing the system in terms of symmetries and fluctuations around local thermodynamic equilibrium. In this formulation, microscopic excitations are repackaged into collective excitations of the system, namely sound and diffusive modes, that transport conserved densities and which are experimentally accessible. In this talk, I show how the Landau criteria appears in the hydrodynamic formulation of superfluidity. For superfluids that flow above some critical velocity, there exist unstable collective excitations that grow exponentially in time. Ultimately, this is connected to a thermodynamic instability that manifests as a divergence in the superfluid velocity's static susceptibility. In Helium-4, where a microscopic description exists, both microscopics and hydrodynamics agree that the critical velocity for the instability is given by the "roton minimum" of the dispersion relation for the massless Goldstone boson associated with the spontaneous symmetry breaking of a global U(1) symmetry. |
Tuesday, March 7, 2023 3:24PM - 3:36PM |
K30.00003: Superfluid He-3 suppression near atomically smooth surfaces Anton Vorontsov Quasiparticle scattering on surfaces is an important mechanism of pairbreaking of unconventional superfluids, and is particularly relevant for superfluids confined to small volumes. Typically, smooth atomic surfaces are thought to be minimally pairbreaking for superfluid He-3 A-phase in thin slabs. We consider scattering on smooth surfaces with lattice periodicity on the order of the Fermi wavelength of He-3, where diffraction effects may lead to strong back-scattering of quasiparticles and significant suppression of the transition temperature. We investigate how the periodic structure and the electronic density corrugation of the surface atomic layer affect the superfluid transition temperature in thin slabs. |
Tuesday, March 7, 2023 3:36PM - 3:48PM |
K30.00004: Vacancy dynamics and magnetism in a two-dimensional Wigner crystal Kyung-Su Kim, Chaitanya Murthy, Steven A Kivelson The two-dimensional Wigner crystal (WC) occurs in the strongly interacting regime of the two-dimensional electron gas. Recently, the present authors showed from the semi-classical instanton calculation that the cooperative hopping processes of interstitial defect of the WC induce a large ferromagnetic polaron with a large energy scale. We extend this work to the vacancy defect of the WC and obtain its effective T=0 dynamics. In contrast to the interstitial defect, vacancy induces paramagnetic (or antiferromagnetic) tendencies around it. From this we speculate on the phases resulting from doping a small density of vacancies in the WC. |
Tuesday, March 7, 2023 3:48PM - 4:00PM |
K30.00005: Goldstone bosons and hydrodynamics with dipole and momentum conservation Xiaoyang Huang, Paolo Glorioso, Andrew Lucas We develop a Schwinger-Keldysh effective field theory describing the hydrodynamics of a fluid with conserved charge and dipole moments, together with conserved momentum. The resulting hydrodynamic modes are highly unusual, including sound waves with magnon-like propagation and subdiffusive decay rate. We show that the momentum density is approximately the Goldstone boson for a dipole symmetry which appears spontaneously broken at finite charge density. Next, we show how to couple the hydrodynamic field theory to the curved spacetime. We remark that the dipole fluid can be regarded as the infinite mass limit of the Galilean-invariant fluid suggesting applications to many-body flat band systems. |
Tuesday, March 7, 2023 4:00PM - 4:12PM |
K30.00006: Marginal metallic state at a fractional filling of '8/5' and '4/3' of Landau levels in the GaAs/AlGaAs 2D electron system Ramesh Mani, U K Wijewardena, Tharanga Nanayakkara, Annika Kriisa, Christian Reichl, Werner Wegscheider A metallic state with a vanishing activation gap, at a filling factor ν = 8/5 in the untilted specimen with n= 2 x 1011 cm-2, and at ν = 4/3 at n=1.2 x 1011 cm-2 under a θ = 660 tilted magnetic field, is examined through a microwave photo-excited transport study of the GaAs/AlGaAs 2 dimensional electron system (2DES). The results presented here suggest, remarkably, that at the possible degeneracy point of states with different spin polarization, where the 8/5 or 4/3 FQHE vanish, there occurs a peculiar marginal metallic state that differs qualitatively from a quantum Hall insulating state and the usual quantum Hall metallic state. Such a marginal metallic state occurs most prominently at ν=8/5, and at ν=4/3 under tilt as mentioned above, over the interval 1 ≤ν≤ 2, that also includes ν= 3/2, which appears perceptibly gapped in the first instance.[1] |
Tuesday, March 7, 2023 4:12PM - 4:24PM |
K30.00007: Drag resistance mediated by quantum spin liquids Raffaele Mazzilli Recent advances in material synthesis made it possible to realize two-dimensional monolayers of candidate materials for a QSL such as αRuCl3,1T-TaSe2 and 1T-TaS2. In this work we propose an experimental setup that exploits non-local electrical probes to gain information on the transport properties of a gapless quantum spin liquid. The proposed setup is a spinon induced drag experiment: a current is injected in one of the two layers and a voltage is measured on the second metallic film. The overall momentum transfer mechanism is a two-step process mediated by Kondo interaction between the local moments in the quantum spin liquid and the spins of the electrons. We develop a model based on the Boltzmann kinetic equation to model the proposed setup. Within this framework we calculate the low temperature scaling behavior of the drag resistivity, both for a U(1) and a Z2 QSL with Fermi surfaces. In some regimes we find a crossover in the temperature scaling that is significantly different between the Z2 and U(1) QSL both because of the non-Fermi liquid nature of the U(1) QSL and because of the qualitatively different momentum relaxation mechanism within the QSL layer. Our findings also suggest that parameters can be tuned to make the spinon induced drag a dominant effect with respect to Coulomb drag. |
Tuesday, March 7, 2023 4:24PM - 4:36PM |
K30.00008: Chester Supersolid of Spatially Indirect Excitons in Double-Layer Semiconductor Heterostructures David Neilson, Sara Conti, Andrea Perali, Alexander R Hamilton, Francois M Peeters, Milorad V Milosevic A supersolid, a counter-intuitive quantum state in which a rigid lattice of particles flows without resistance, has to date not been unambiguously realized. Here we reveal a supersolid ground state of excitons, formed from electrons and holes that are spatially separated in a double-layer semiconductor heterostructure. The supersolid spans a wide range of layer separations lying outside the focus of recent transport experiments on exciton superfluidity in these systems [1]. Our supersolid conforms to the original Chester concept of a supersolid [2] with one exciton per supersolid site. It is distinct from alternative versions observed in cold-atom systems which are characterized by a periodic modulation of the superfluid density [3]. We provide the phase diagram, augmented by the supersolid. This new phase appears at layer separations much smaller than the predicted exciton normal solid [4], and it persists up to a solid-solid transition where the quantum phase coherence collapses while leaving the translational symmetry preserved. The ranges of layer separations and exciton densities in our phase diagram are well within reach of current experimental capabilities. |
Tuesday, March 7, 2023 4:36PM - 4:48PM |
K30.00009: Boundary theory of the X-cube model in the continuum Ryan Spieler I study the boundary theory of the X-Cube model on T2xI from the perspective of continuum field theory. The boundary theory contains information about the statistics of a subset of the bulk excitations, and admits gapping terms that either break or preserve rotation and translation symmetries of the boundary. I discuss the computation of the ground state degenracy of the system with a gapped boundary, which is highly sensitive to boundary conditions. I also discuss the anomaly inflow of the mixed 't Hooft anomaly on the boundary, and find that the X-Cube is not the only theory that cancels it. I then discuss more complicated boundary terminations and their consequences. |
Tuesday, March 7, 2023 4:48PM - 5:00PM Author not Attending |
K30.00010: Coexistence of two hole-phases in the vicinity of filling factors 1 and 1/3 in p-GaAs/AlGaAs studied by acoustic method Alexey Suslov, Irina L Drichko, Ivan Y Smirnov, Kirk W Baldwin, Loren N Pfeiffer, Ken West, Yuri M Galperin We studied ac conductivity in a 17 nm wide single p-GaAs/AlGaAs quantum well with hole concentration ~1.2×1011 cm−2 and mobility ~1.8×106 cm2/Vs. The ac conductivity σac=σ1 - iσ2 was calculated from simultaneously measured absorption and velocity of surface acoustic waves (SAWs) propagating parallel to the well. Measurements, performed at SAW frequency 30 – 300 MHz and temperatures 20 – 300 mK, exhibited integer and fractional quantum Hall (QH) effects in magnetic fields. Analysis of the σ1 and σ2 shows that at the filling factor ν = 1 the carriers are localized in the minima of random potential with single-carrier hoppings between localized states, whereas at ν = 1/3 the carrier state corresponds to incompressible liquid. When ν deviates from 1 and 1/3, the temperature and frequency dependencies of σ1, σ2, and σ1/σ2 gradually change and become drastically modified. We link this evolution to the formation of domains of the Wigner solid which are most pronounced at the lowest temperature at ν equal to 1.2 and 0.78, as well as 0.375 and 0.3. When the temperature rises, the domains melt as concluded by studying the frequency dependencies of σ2. We explain the lack of sharp transitions in the conductivity behaviors by the coexistence of the QH-related hole states and Wigner domains. |
Tuesday, March 7, 2023 5:00PM - 5:12PM |
K30.00011: Observation of Re-entrant Correlated Insulators at One Magnetic Flux Quantum per Moiré Unit Cell in Magic-Angle Twisted Bilayer Graphene Ipsita Das The discovery of flat bands with nontrivial band topology in magic-angle twisted bilayer graphene (MATBG) has provided a unique platform to study strongly correlated phenomena including superconductivity, correlated insulators, Chern insulators, and magnetism. A fundamental feature of the MATBG, so far unexplored, is its high magnetic field Hofstadter spectrum. Here, we report on a detailed magnetotransport study of a MATBG device in external magnetic fields of up to B = 31 T, corresponding to one magnetic flux quantum per moire unit cell Φ0. At Φ0, we observe reentrant correlated insulators at a flat band filling factors of ν = +2 and of ν = +3, and interaction-driven Fermi-surface reconstructions at other fillings, which are identified by new sets of Landau levels originating from these. These experimental observations are supplemented by theoretical work that predicts a new set of eight well-isolated flat bands at Φ0, of comparable band width, but with different topology than in zero field. Overall, our magnetotransport data reveal a qualitatively new Hofstadter spectrum in MATBG, which arises due to the strong electronic correlations in the reentrant flat bands. |
Tuesday, March 7, 2023 5:12PM - 5:24PM Author not Attending |
K30.00012: Disentangling photodoping, photoconductivity and photosuperconductivity in the cuprates Ralph El Hage, Vincent Humbert, Victor Rouco, Anke Sander, Fabian Cuellar, David Sanchez-Manzano, Juan Trastoy, Jacobo Santamaria, Javier E Villegas, Kevin Seurre, Aurélien LAGARRIGUE, Javier BRIATICO Persistent photoconductivity (PPC) and persistent photo-superconductivity (PPS) describe both the enhancement of the conductivity and the increase of the superconducting transition temperature (Tc) of cuprate superconductors upon visible and UV light illumination. The debate on the microscopic origin of those effects has not been settled, but the existing models assume a link between them and the concomitant carrier-density enhancement (photodoping). Here we present experiments that show that, contrary to conventional wisdom, the enhancement of Tc correlates instead with a reduction of the impurity scattering rate. Since this decrease in scattering rate and the photoinduced increase in carrier density exhibit different wavelength and oxygen-content dependence, as well as contrasting relaxation dynamics we conclude a decoupling of these two parameters. Besides shedding light on the entanglement of PPS and PPC, our results provide new evidence on the intimate relationship between carrier mobility and critical temperature which promises to provide new insights into the mechanism at the heart of high Tc superconductivity. |
Tuesday, March 7, 2023 5:24PM - 5:36PM |
K30.00013: Planckian scattering rate from coherent charge carrier-lattice vibration dynamics Alhun Aydin, Eric J Heller Fermi liquid and Bloch-Grüneisen theories fail to describe strange metal behaviors, e.g. normal state properties of high Tc superconductors. Cuprates, heavy Fermion materials and twisted bilayer graphene exhibit universal linear-in-temperature resistivity which can be obtained by Drude formula with the Planckian scattering rate. Consisting of only Planck and Boltzmann constants, this mysterious scattering rate has eluded explanations. Here we show that a Planckian scattering rate emerges from coherent and non-perturbative interactions of charge carriers and lattice vibrations. Carrier velocities are slowed down due to the strong deformation potential scattering. Two competing mechanisms emerge in this regime: A strong deformation potential tries to localize carriers, but its dynamics (random movement and shape-shifting) induces delocalization. We find that carrier diffusion saturates to the previously conjectured quantum bound of diffusion. We obtain the Planckian scattering rate from the quantum diffusion of carriers and correctly predict the experimentally observed universal linear-in-temperature resistivity for various cuprates. |
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