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 T30: Strongly Correlated Systems, Including Quantum Fluids and Solids XVIII |
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Sponsoring Units: DCMP Chair: Haim Beidenkopf, Weizmann Institute of Science Room: Room 222/223 |
Thursday, March 9, 2023 11:30AM - 11:42AM |
T30.00001: Asymptotic sign free in interacting fermion models Zixiang Li As an intrinsically-unbiased method, quantum Monte Carlo (QMC) is of vital importance in understanding correlated phases of matter. Unfortunately, it often suffers notorious sign problem when simulating interacting fermion models. Here, we show for the first time that there exist interacting fermion models whose sign problem are less severe for larger system sizes and eventually disappears in the thermodynamic limit, which we dub as ``asymptotic sign free'' (ASF). We demonstrate asymptotically-free sign for various interacting models featuring Dirac fermions by determinant QMC. The numerical results offer unambiguous examples showing the asymptotically free behavior of sign problem in different models. Moreover, based on renormalization group ideas we propose an heuristic understanding of this novel feature of asymptotic sign-free. We believe that the asymptotic sign free behavior will shed new lights on deeper understanding of sign problem, and more importantly, applying QMC to deciphering quantum many-body physics in broader strongly correlated systems. |
Thursday, March 9, 2023 11:42AM - 11:54AM |
T30.00002: Exact solution of the transverse field Sherrington-Kirkpatrick spin glass model with continuous-time quantum Monte Carlo method Izabella Lovas, Annamaria Kiss, Catalin Pascu Moca, Gergely Zarand We obtain the exact numerical solution of the transverse field Sherrington-Kirkpatrick quantum spin glass model, by implementing the continuous-time Monte Carlo method in the presence of full replica symmetry breaking. We extract the complete numerically exact phase diagram, displaying a glassy phase with continuous replica symmetry breaking at small transverse fields and low temperatures. A paramagnetic phase emerges once thermal and quantum fluctuations melt the spin glass. We characterize both phases by extracting the order parameter, as well as the static and dynamical local spin susceptibilities. The static susceptibility shows a plateau in the glassy phase, but remains smooth across the phase boundary, while the shape of dynamical susceptibility varies upon crossing the glass transition by reducing quantum fluctuations. We qualitatively compare these results to the susceptibility observed experimentally in dipole-coupled Ising magnets in a transverse magnetic field. Our work provides a general framework for the exact numerical solution of mean field quantum glass models, constituting an important step towards understanding glassiness in realistic systems. |
Thursday, March 9, 2023 11:54AM - 12:06PM |
T30.00003: Tricritical Ising Phase Transition in a Ladder of Josephson Junction Array. Lorenzo Maffi, Michele Burrello, Matteo Rizzi Tricritical Ising phase transition (TCI) is known to occur in several quantum many body systems like interacting spin models and Rydberg atom chains. In 1D its operator content is described by the conformal field theory which predicts the presence of 4 relevant operators and among them the Fibonacci field. However, not so many experimental realizations of TCI have been performed in the past. We will present a 2-legs ladder of hybrid superconductor-semiconductor Josephson Junction (JJ) array that displays such tricritical phase diagram. The two legs are coupled at each rung by mean of three parallel JJs leading to an interesting on site interaction. The semiclassical phase diagram hosts a tricritical line and a TCI is expected in the quantum regime once charging energy is taken into account. In particular, a three-frequency Sine-Gordon model arises in the bosonized description. By using the Landau-Ginzburg formulation of the conformal minimal model, possible signatures of operator contents of the conformal field theory are discussed. Furthermore, the thermal response sheds light on the ladder tricritical Ising behaviour once the phase transition is crossed and leads to a quantitative measurement of the central charge. |
Thursday, March 9, 2023 12:06PM - 12:18PM |
T30.00004: Re-investigation of the ground state phases of the one-dimensional half filled Hubbard-Holstein model Sam Mardazad, Martin Grundner, Ulrich Schollwöck, Adrian Katian, Thomas Köhler, Sebastian Paeckel % |
Thursday, March 9, 2023 12:18PM - 12:30PM |
T30.00005: Non-analytic localization length at the metal-insulator phase transition in the Hubbard-Holstein model Sebastian Paeckel, Sam Mardazad, Martin Grundner, Thomas Koehler Recently, theoretical and methodical advances generated re-increased interest in the interplay between strongly correlated electrons and quantized lattice vibrations (phonons). While non-local couplings give rise to various new phenomena, such as high-TC phonon-mediated superconductivity (arXiv:2203.07380), the phase diagram of the protoypic Hubbard-Holstein model featuring a local electron-phonon coupling only is still far from being completely understood. In particular, this is the case in the regime where electron-electron and electron-phonon interactions are comparable to the phonon frequency, a regime in which a metallic phase is known to exist. Using recent developments in the field of tensor network methods, we reinvestigated the transition from the metallic into the insulating, charge ordered phase. Here, large-scale numerics allows us to carefully identify and resolve finite-size effects, allowing for a high precision calculation of generically challenging quantities, such as the localization length, or the central charge. Our findings reveal a novel perspective to the microscopic origin of the phase transition from a metallic into the insulating phase. |
Thursday, March 9, 2023 12:30PM - 12:42PM |
T30.00006: Unusual doping-dependent sign changes of the Seebeck coefficient in strongly correlated systems Sayantan Roy, Thereza Paiva, Willdauany C de Freitas Silva, Maykon V Araujo, Abhisek Samanta, Natanael C Costa, Nandini Trivedi The thermoelectric performance of a material is determined by its Seebeck coefficient, or the thermopower which may be enhanced, among other sources, by strong electronic correlations. In view of this, we investigate the Seebeck coefficient for the two-dimensional repulsive Fermi Hubbard model on different geometries (square, triangular, and honeycomb lattices). We employ Determinant Quantum Monte Carlo as an unbiased numerical technique to investigate the behavior of the Seebeck coefficient as a function of particle doping. Our analysis is conducted in weak to strong interaction regimes, that includes the critical point for onset of Mott physics. The DQMC simulation is performed at high enough temperatures to alleviate the sign problem and preclude spontaneous symmetry breaking. We interpret the DQMC data from a mean-field perspective, employing a Hartree Fock mean-field for the weak coupling regime and Parton mean-field theory for the strong coupling regime. Our analysis indicates that the non-trivial sign change and the singularities in the Seebeck coefficient (compared to the noninteracting case) can be attributed to the charge physics brought by the onset of the "Mottness" of the system. |
Thursday, March 9, 2023 12:42PM - 12:54PM |
T30.00007: Random geometry at an infinite-randomness fixed point Akshat Pandey, Aditya Mahadevan The critical one-dimensional random transverse-field Ising model is a paradigmatic example of a system whose low-energy physics is governed by an infinite-randomness fixed point, for which many results on the distributions of couplings are known via an asymptotically exact renormalization group (RG) approach. In two dimensions, the same RG rules can be implemented numerically, and demonstrate a flow to infinite randomness. However, theoretical understanding remains elusive due to the development of geometrical structure in the graph of interacting spins. To better understand the character of the fixed point, we consider the RG flow acting on a joint ensemble of graphs and couplings, and characterize the statistics of the geometry that emerges at the infinite-randomness fixed point, with a combination of numerical and simplified analytical RGs. |
Thursday, March 9, 2023 12:54PM - 1:06PM |
T30.00008: Boundary phenomena and phase transitions in strongly correlated one dimensional systems. Parameshwar R Pasnoori, Junhyun Lee, Jedediah H Pixley, Yicheng Tang, Patrick Azaria, Natan Andrei One dimensional quantum systems exhibit many interesting physical phenomena as a result of strong correlations. The gapped systems with symmetries exhibit exotic phases and are categorized as spontaneous symmetry breaking (SSB) or symmetry protected topological (SPT) phases. Systems with SSB have non vanishing local order parameter and a discrete symmetry is spontaneously broken leading to degenerate pairing in the spectrum. In contrast, systems with SPT exhibit non-local order parameter and robust ground state degeneracy associated with protected fractionalized gapless excitations at the edges. In this work we consider systems belonging to both classes: the spin 1/2 XXZ chain which exhibits SSB and the charge conserving superconductor which exhibits SPT, and study them under the effect of symmetry breaking fields at the edges. We find that these systems exhibit a rich phase diagram and show that certain phases display spin fractionalization associated with strong Majorana zero modes at the edges. We then consider spin 1/2 Heisenberg XXX chain, a gapless system that does not fall into either the SPT or SSB classes. We show that it exhibits a rich phase diagram and contains zero modes which arise at high energies. We show that in all three systems described above, the Hilbert space is comprised of a certain number of towers of excited states, and that they exhibit a new type of phase transition named 'Hilbert space' or 'eigenstate' phase transition where the number of towers of the Hilbert space changes as result of the application of the edge fields. |
Thursday, March 9, 2023 1:06PM - 1:18PM |
T30.00009: Multiversality of charge density wave onset in a Luttinger liquid Changnan Peng It has been recently realized that the universality class of a continuous transition between two phases of matter may not be unique: different regions of the phase boundary may realize distinct universality classes. We describe an example of such multiversality: a transition from a 1d Luttinger liquid to a charge density wave insulator. We show that while part of the boundary between these two phases realizes the Kosterlitz-Thouless transition (central charge $c = 1$, Luttinger parameter $K=1/2$), another part is descibed by an Ising transition coexisting with the Luttinger liquid (central charge $c = 1/2+1$ and variable Luttinger parameter). We demonstrate these conclusions using analytical renormalization group calculations, as well as numerical density martrix renormalization group simulations of a concrete microscopic model. |
Thursday, March 9, 2023 1:18PM - 1:30PM |
T30.00010: Boundary deconfined quantum criticality at transitions between symmetry-protected topological chains Saranesh Prembabu, Ruben Verresen, Ryan Thorngren A Deconfined Quantum Critical Point (DQCP) is an exotic non-Landau transition between distinct symmetry-breaking phases, with many 2+1D and 1+1D examples. We show that a DQCP can occur in zero spatial dimensions, as a boundary phase transition of a 1+1D gapless system. Such novel boundary phenomena can occur at phase transitions between distinct symmetry-protected topological (SPT) phases, whose protected edge modes are incompatible and compete at criticality. We consider a minimal symmetry class Z3×Z3 which protects two non-trivial SPT phases in 1+1D. Tuning between these, we find a critical point with central charge c=8/5 and two stable boundary phases spontaneously breaking one of the Z3 symmetries at the 0+1D edge. Subsequently tuning a single boundary parameter leads to a direct continuous transition -- a 0+1D DQCP, which we show analytically and numerically. Similar to higher-dimensional cases, this DQCP describes a condensation of vortices of one phase acting as order parameters for other. Moreover, we show that it is also a Delocalized Quantum Critical Point, since there is an emergent symmetry mixing boundary and bulk degrees of freedom. This work suggests that studying criticality between non-trivial SPT phases is fertile soil and we discuss how it provides insights into the burgeoning field of gapless SPT phases. |
Thursday, March 9, 2023 1:30PM - 1:42PM |
T30.00011: Microscopic Magnetic Characterization of Quantum Criticality in LaCrGe3 using 139La NMR under Pressure Khusboo Rana, Hisashi Kotegawa, Rahim R Ullah, Elena Gati, Sergey L Bud'ko, Paul C Canfield, Hideki Tou, Valentin Taufour, YUJI FURUKAWA LaCrGe3 is a peculiar itinerant ferromagnet with a unique route to avoid a ferromagnetic quantum critical point (QCP) by not only changing the order of the phase transition from second to first, but also through the appearance of a high-pressure magnetic phase. Expanding on earlier work which suggested that the high-pressure magnetic phase could be a short-range magnetically ordered cluster phase, 139La nuclear magnetic resonance (NMR) measurements were carried out under pressure up to 2.64 GPa. The NMR spectrum measurements suggest that a ferromagnetic order develops below 50 K at pressures higher than ~1.5 GPa under the applied magnetic field of 7.2 T. Furthermore, three-dimensional ferromagnetic fluctuations were found in the paramagnetic state which persisted even at high pressures close to the putative QCP. These findings provide a novel insight into the quantum criticality of this system. |
Thursday, March 9, 2023 1:42PM - 1:54PM |
T30.00012: Characterizing phases of the two dimensional repulsive Fermi Hubbard model using local correlators Sayantan Roy, Sameed Pervaiz, Thomas R Hartke, Abhisek Samanta, Martin W Zwierlein, Thereza Paiva, Nandini Trivedi Cold atom systems provide a rich platform to realize strongly interacting condensed matter systems, and recent progress in fluorescence imaging technique [1,2] has enabled identification of non-trivial doublon, singlon and holon correlation functions. We report a DQMC study of such correlation functions in the two dimensional repulsive Fermi Hubbard model as a function of density, in corroboration with recent experimental findings [2]. We identify density-dependent suppression of holon-holon and doublon-doublon correlations. On the other hand, the singlon correlations with other singlon, or with holons and doublons, show non-trivial density dependent structure. We provide a parton construction which allows us to get insights into the nature of these different correlations. |
Thursday, March 9, 2023 1:54PM - 2:06PM |
T30.00013: Analytical and numerical studies of phases of systems with spatially modulated symmetries Pablo Sala de Torres-Solanot, Yizhi You, Olexei I Motrunich In recent years, systems with unconventional symmetries have attracted a lot of attention due to the wealth of exotic phenomena they display. In particular, the role of multipole-moment and subsystem symmetries have been explored extensively. Both of these have been shown to lead to exotic low-energy features including fracton phases of matter, fractal quantum criticality, Bose surfaces and UV/IR-mixing among other phenomena. In this talk, we will study a family of bosonic one-dimensional models, which conserve |
Thursday, March 9, 2023 2:06PM - 2:18PM |
T30.00014: Quantum criticality on a compressible lattice. Saheli Sarkar, Markus Garst, Lars Franke, Niko Grivas As an example of quantum criticality on a compressible lattice we study the Lorentz invariant Φ4 theory with an N-component field Φ, where strain couples to the square of the order parameter. In three spatial dimensions this coupling as well as the self-interaction of the Φ field are both marginal on the tree-level. We compute the one-loop renormalization group equations treating the Φ field as well as the phonons on the same footing. We find that the velocities of the Φ field as well as of the phonons are renormalized yielding an effective dynamical exponent z > 1. The renormalization group flow is found to depend on the number of components N. Whereas we find run-away flow for N < 4 a new fixed-point emerges for N >= 4. We discuss the relation to known results for classical criticality. Our findings are directly relevant to insulating quantum critical antiferromagnets |
Thursday, March 9, 2023 2:18PM - 2:30PM |
T30.00015: Statistics induced phase transitions in the extended bosonic anyon Hubbard model Martin Bonkhoff, Imke Schneider, Kevin Jägering, Axel Pelster, Shi-Jie Hu, Sebastian Eggert We study a 1D extended Hubbard model of anyons with statistical exchange phases ranging from bosons to pseudo-fermions. The model can be realized in optical lattice experiments implementing occupation-dependent hopping amplitudes. We enforce a two-body hard-core constraint and numerically determine the full phase diagram including attractive on-site interactions. Surprisingly, the symmetry protected topological Haldane phase remains robust up to large statistical angles close to the pseudo-fermionic limit. However, for a critical angle the phase diagram qualitatively changes involving a dimer phase while the Haldane phase disappears. This behavior is analytically described by an adapted bosonization approach. |
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