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 W29: Strongly Correlated Systems, Including Quantum Fluids and Solids XIX |
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Sponsoring Units: DCMP Chair: Federico Roccati, University of Luxembourg Room: Room 221 |
Thursday, March 9, 2023 3:00PM - 3:12PM |
W29.00001: Many-body localized to ergodic transitions in a system with correlated disorder Abhisek Samanta, Ahana Chakraborty, Rajdeep Sensarma We study the many-body localization (MBL) to ergodic phase transition in a simple model of correlated disorder in a spin chain, which can be tuned from an uncorrelated to an extremely correlated limit using a single parameter. Using several statistical measures, like gap-statistics and extremal entanglement spectrum distributions, we find the phase diagram in the the disorder-correlation plane. We show that one can use the average of sample variance of disorder as a single parameter which encodes the effects of the correlated disorder, and hence the distributions and averages of various statistics collapse into a single curve as a function of this parameter. This also allows us to analytically calculate the phase diagram in the disorder-correlation plane. |
Thursday, March 9, 2023 3:12PM - 3:24PM |
W29.00002: New fixed points of coupled spin chains Kaixiang Su, Shang Liu, Cenke Xu In this work we investigate the effect of long-range interactions on critical theories preserving certain symmetries. M copies of SU(N)1 WZW models are coupled with general terms that respect the chiral SU(N) and a Z_M permutation symmetry. To mimic the long-range interactions, a non-local boson is introduced that couples to the order parameter of the individual chains. We derive the RG equations in certain limits where both M and N are large. We then find two fixed points: a stable fixed point decoupled from the external non-local boson, and another critical point that separates a Neel phase induced by the long-range interaction and the stable fixed point. The scaling exponents at the critical points are calculated, and relations to known conformal field theories are discussed. Our work shed light on long-range interaction induced fixed point and boundary criticality problems. |
Thursday, March 9, 2023 3:24PM - 3:36PM |
W29.00003: Fermi edge singularity in absorption spectra of cold neutral electron-hole system Erik A Szwed, Darius J Choksy, Leonid V Butov, Kirk W Baldwin, Loren N Pfeiffer We studied ultracold neutral electron-hole (e-h) systems in separated electron and hole layers in GaAs/AlGaAs coupled quantum well heterostructure. The long e-h lifetimes due to the layer separation allow the e-h systems to cool to low temperatures. We found a strong enhancement of the spatially indirect photoluminescence at the Fermi energy of the ultracold plasma, the evidence of the excitonic Fermi edge singularity due to the Cooper-pair-like excitons at the Fermi energy. We also found a strong enhancement of the spatially direct absorption at the Fermi energy of the ultracold plasma. The absorption was probed by photoluminescence excitation spectroscopy of the spatially indirect photoluminescence. We controlled the e-h density by the laser excitation power and, with the increasing e-h density, observed a crossover from the absorption of hydrogen-like excitons at low e-h densities to the Fermi edge singularity in absorption at high e-h densities. |
Thursday, March 9, 2023 3:36PM - 3:48PM |
W29.00004: Microscopic study of a complex conformal theory in the O(n) loop model in 2D Omid Tavakol, Arijit Haldar, Han Ma, Adam Nahum, Thomas Scaffidi The presence of nearby conformal field theories (CFTs) hidden in the complex plane of the tuning parameter was recently proposed as an elegant explanation for the ubiquity of "weak" first order transitions in condensed matter and high-energy systems. However, studying such complex CFTs is even more challenging than for real CFTs, and few results exist about them. In this work, we present an exact microscopic study of a complex CFT (CCFT) for a loop formulation of the O(n) model in 2D. Thanks to a numerical finite-size study of the transfer matrix, we locate the CCFT in the complex plane and extract the real and imaginary part of the central charge and scaling dimensions. By comparing those with the analytic continuation of predictions from Coulomb gas techniques, we determine the range of validity of the analytic continuation to extend up to n∼13, beyond which the CCFT disappears. Finally, we propose an approximate real-space renormalization group model which reproduces the main features of the spiral RG flow around the CCFTs. |
Thursday, March 9, 2023 3:48PM - 4:00PM |
W29.00005: Tilt-induced transformations of fractional quantum Hall effects U. Kushan Wijewardena, Tharanga R Nanayakkara, Annika Kriisa, Christian Reichl, Werner Wegscheider, Ramesh Mani Two-dimensional electron systems subjected to high transverse magnetic fields can exhibit Fractional Quantum Hall Effects (FQHE). In the GaAs/AlGaAs 2D electron system, a double degeneracy of Landau levels due to electron-spin, is removed by a small Zeeman spin splitting, gμBB, comparable to the correlation energy. Then, a change of the Zeeman splitting relative to the correlation energy can lead to a re-ordering between spin polarized, partially polarized, and unpolarized many body ground states at a constant filling factor. We show here that tuning the spin energy can produce fractionally quantized Hall effect transitions that include both a change in ν for the Rxx minimum, e.g., from ν = 11/7 to ν = 8/5, and a corresponding change in the Rxy, e.g., from Rxy/RK = (11/7)-1 to Rxy/RK = (8/5)-1, with increasing tilt angle. Further, we exhibit a striking size dependence in the tilt angle interval for the vanishing of the ν = 4/3 and ν = 7/5 resistance minima, including "avoided crossing" type lineshape characteristics, and observable shifts of Rxy at the Rxx minima- the latter occurring for ν = 4/3, 7/5 and the 10/7. The results demonstrate both size dependence and the possibility, not just of competition between different spin polarized states at the same ν and Rxy, but also the tilt- or Zeeman-energy-dependent- crossover between distinct FQHE associated with different Hall resistances.[1] |
Thursday, March 9, 2023 4:00PM - 4:12PM |
W29.00006: Gapless States with Generalized Symmetries and Large Conserved Quantities Xiaochuan Wu, Chao-Ming Jian, Wenjie Ji, Cenke Xu We investigate the behavior of generalized symmetries in various gapless systems. To unambiguously characterize whether symmetry is spontaneously broken or not, we introduce the concept of "order diagnosis operator" (ODO). We first consider discrete 1-form symmetries at quantum phase transitions, which can be either part of "categorical symmetry" introduced recently or an explicit 1-form symmetry. We discuss the universal term in ODOs for Z_N 1-form symmetries. Then we move to systems with a large number of conserved quantities, such as fermi-surface states and systems with subsystem symmetries. The special features of ODOs in some examples will be mentioned. |
Thursday, March 9, 2023 4:12PM - 4:24PM |
W29.00007: Deconfined quantum critical point with nonlocality Yichen Xu, Xiaochuan Wu, Cenke Xu The deconfined quantum critical point (DQCP) between the Néel and valence bond solid order was originally proposed in quantum spin systems with a local Hamiltonian. In the last few years analogs of DQCPs with nonlocal interactions have been explored, which can lead to rich possibilities. The nonlocal interactions can either arise from an instantaneous long-range interaction in the Hamiltonian, or from gapless modes that reside in one higher spatial dimension. Here, we consider another mechanism of generating nonlocal interactions by coupling the DQCP to the "hot spots" of a Fermi surface. We demonstrate that at least within a substantial energy window, the physics of the DQCP is controlled by a new fixed point with a dynamical exponent z>1. |
Thursday, March 9, 2023 4:24PM - 4:36PM |
W29.00008: Effect of measurements on the entanglement entropy of critical ground states in 1+1d Zhou Yang, Chao-Ming Jian, Dan Mao Measurement provides a powerful tool to manipulate quantum information in a quantum many-body system. In particular, it has been shown that measurements on particular quantum states can help carry out quantum computations and prepare new quantum states with long-range entanglement. For this work, we focus on the effect of measurements on the entanglement within the ground states of various one-dimensional critical systems. Before measurements, such a critical ground state can be viewed as the ground state of a 1+1d conformal field theory (CFT), whose entanglement entropy (EE) is known to scale as the logarithm of the subsystem size $L$ with the prefactor proportional to the central charge $c$. After measurements, we demonstrate that when the measurement leads to a relevant perturbation, the EE is reduced from the logarithmic scaling to an area law even if the correlation functions on the post-measurement state still follow a power law, suggesting a diverging correlation length. More interestingly, when the perturbation induced by the measurement is exactly marginal, the EE retains the logarithmic scaling $S_A = frac{c_ ext{eff}}{3} log(L)$ but with a continuously tunable effective central charge $0 |
Thursday, March 9, 2023 4:36PM - 4:48PM |
W29.00009: Site-selective correlations in strongly-interacting quasicrystals Yuxi Zhang, Richard T Scalettar, Rafael M Fernandes Quasicrystals provide an interesting framework to study interacting flat-band systems, due to the existence of a geometrically-enforced macroscopic number of zero-energy states. Here, we present quantum Monte Carlo (QMC) simulations of the Hubbard model on quasicrystals with different types of tilling. We investigate the behavior of the imaginary time Green’s functions G(i,τ=β/2), which acts as a proxy of the local spectral function Az(ω), on sites (orbitals) with different coordination number z. A "site-selective" behavior is found, where data for G(i,τ=β/2) for sites i with different z exhibit a crossing point T* as the temperature T is varied. By tracking T* as a function of the Hubbard interaction U, which controls the quantum critical behavior, the quantum phase transition can be located by identifying the value of U* for which T*(U) → 0. We compare the estimated U* directly with the Uc value extracted from the behavior of the specific heat C(T) for different types of quasicrystals. |
Thursday, March 9, 2023 4:48PM - 5:00PM |
W29.00010: The one-dimensional Holstein model revisited Sijia Zhao, Zhaoyu Han, Ilya Esterlis, Steven A Kivelson We analyze the global ground-state (quantum) phase diagram of the one-dimensional Holstein model at half-filling as a function of the strength of the electron-phonon coupling (represented by the strength of the phonon-induced attraction, $U$) and the phonon frequency, $omega_0$. In addition to reanalyzing the various asymptotic regimes, we have carried out density-matrix renormalization group simulations to correct previous inferences concerning the anti-adiabatic (large $omega_0$) and strong coupling (large $U$) regimes. |
Thursday, March 9, 2023 5:00PM - 5:12PM |
W29.00011: Hydrodynamic charge transport in ultrahigh-mobility two-dimensional electron gas Xinghao Wang, Yu-jiang Dong, Peizhe Jia, Loren N Pfeiffer, Kirk W Baldwin, Ken West, Rui-Rui Du Viscous fluid in an ultrahigh-mobility (between 2 to 3*10^7 cm^2/Vs) two-dimensional electron gas (2DEG) in GaAs/AlGaAs quantum wells was systematically studied through measurements of negative magnetoresistance (NMR) and photoresistance under microwave radiation, and the data were analyzed according to recent theoretical works by e.g., Alekseev, Physical Review Letters 117,166601 (2016). Size-dependent and temperature dependent NMR were found to conform to the theoretical predictions. The size dependence of microwave induced resistance oscillations (MIRO) and that of the ‘2nd harmonic’ peak indicate that 2DEG in a moderate magnetic field should be regarded as viscous fluid as well. Our results suggest that the hydrodynamic effects must be considered in order to understand semiclassical electronic transport in a clean 2DEG. |
Thursday, March 9, 2023 5:12PM - 5:24PM |
W29.00012: Non-local microwave electrodynamics in ultra-pure PdCoO2 Graham Baker, Timothy Branch, Jake S Bobowski, James Day, Davide Valentinis, Mohamed Oudah, Philippa H McGuinness, Seunghyun Khim, Piotr Surowka, Yoshiteru Maeno, Roderich Moessner, Joerg Schmalian, Andrew Mackenzie, Douglas A Bonn The exceptionally long electronic mean free path in PdCoO2 enables the exploration of novel transport regimes. Using a model developed for two-dimensional electron gases (2DEGs), mesoscopic DC transport experiments in PdCoO2 were interpreted as evidence for viscous effects arising from momentum-conserving (MC) scattering [1]. However, it was recently shown that PdCoO2 exhibits novel directional ballistic transport, beyond that observable in 2DEGs, owing to its nearly-hexagonal Fermi surface (FS) [2]. To understand the combined effects of FS anisotropy and MC scattering, we measured the microwave electrodynamics of PdCoO2 in several sample geometries—introducing the skin effect as a novel, highly-tunable tool for studying non-Ohmic transport [3,4]. From symmetry alone, differences between geometries imply that our results are neither Ohmic nor purely viscous. In conjunction with Boltzmann calculations, we show that the qualitative behavior of the data stems from a novel form of ballistic skin effect owing to the strongly-faceted FS. A quantitative comparison of theory and experiment gives evidence for MC scattering. |
Thursday, March 9, 2023 5:24PM - 5:36PM |
W29.00013: A hydrodynamic description for transport in the strange metal phase of cuprates Daniel K Brattan, Andrea Amoretti, Martina Meinero, Federico Caglieris, Enrico Giannini, Marco Affronte, Christian Hess, Bernd Büchner, Nicodemo Magnoli, Marina Putti, Luca Tomarchio, Nadia Stegani High temperature superconductors are strongly coupled systems which makes it difficult to isolate the mechanism governing their singular transport properties. In strongly coupled systems one generically expects short equilibration times meaning that only long lived degrees of freedom are important. Hydrodynamics is the framework for describing such degrees of freedom. Because hydrodynamics mostly relies on the symmetries of the system, without referring to any specific microscopic mechanism, it constitutes a promising approach for analysing these materials. |
Thursday, March 9, 2023 5:36PM - 5:48PM |
W29.00014: Hydrodynamics with Helical Symmetry Jack Farrell We present the hydrodynamics of fluids in three spatial dimensions with helical symmetry, wherein |
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