Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session D64: Quantum Phase TransitionsRecordings Available
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Sponsoring Units: DCMP Chair: Ian Hayes, University of Maryland Room: Hyatt Regency Hotel -Grant Park B |
Monday, March 14, 2022 3:00PM - 3:12PM |
D64.00001: Phases and phase transitions of a disordered quantum clock model Gaurav R Khairnar, P. K. Vishnu, Ambuj Jain, Pranay M Patil, Rajesh Narayanan, Thomas Vojta We investigate the effects of quenched randomness on the phase diagram and the phase transitions of the quantum clock model. To this end, we map the model onto a (1+1)-dimensional classical spin Hamiltonian with correlated disorder which we study by means of large-scale Monte-Carlo simulations. For weak randomness, the model features an emerging quasi-long-range ordered XY phase that separates the symmetry-broken long-range ordered phase from the disordered phase. With increasing randomness, the XY phase shrinks and vanishes in a tricritical point. Along all phase boundaries, we characterize the critical behaviors and relate them to the Harris Criterion, strong-disorder renormalization group predictions [1], as well as the properties of disorderd rotor Hamiltonians [2]. |
Monday, March 14, 2022 3:12PM - 3:24PM |
D64.00002: Spin-Phonon Resonances in Nearly Polar Metals with Spin-Orbit Coupling Abhishek Kumar, Premala Chandra, Pavel A Volkov In metals in the vicinity of a polar transition, interactions between electrons and soft phonon modes remain to be determined. Here we explore the consequences of spin-orbit assisted electron-phonon coupling on the collective modes of such nearly polar metals in the presense of magnetic field. We find that the soft polar phonon hybridizes with spin-flip electronic excitations of the Zeeman-split bands leading to an anticrossing. The associated energy splitting allows for an unambiguous determination of the strength of the spin-orbit mediated coupling to soft modes in polar metals by spectroscopic experiments. The approach to the polar transition is reflected by the softening of the effective g-factor of the hybridized spin-flip mode. Analyzing the static limit, we find that the polar order parameter can be oriented by magnetic field. This provides possibilities for new switching protocols in polar metallic materials. We demonstrate that the effects we predict can be observed with current experimental techniques and discuss promising material candidates. |
Monday, March 14, 2022 3:24PM - 3:36PM |
D64.00003: Quantum electrodynamics of a dissipative phase transition in a Josephson junction Roman Kuzmin, Nitish Mehta, Nicholas Grabon, Amir Burshtein, Moshe Goldstein, Vladimir Manucharyan It is conventional to rely on dc resistance and its scaling with temperature when assigning a system into the class of superconductor or insulator. However, for a Josephson junction in an ohmic environment, the conventional approach has failed to produce a definite answer. As a result, the existence of a dissipative phase transition between the superconducting and the insulating behavior of a Josephson junction remains controversial. Here, instead of measuring the junction's resistance, we study how the junction elastically and inelastically scatters the environmental photons. Instead of ohmic resistance, our environment is a Josephson transmission line with a non-dissipative wave impedance, the value of which we can tune. We probe the system at the single photon level and measure the junction's reflection coefficient at frequencies exceeding the temperature. Finally, we could follow the scaling of the reflection coefficient by tuning the probe's frequency, which is more reliable than the temperature. Our approach allows us to separate the superconducting and the insulating behavior of a Josephson junction. As the environment's impedance goes up, the junction looks more and more like a capacitor to the reflecting photons, revealing the junction's insulating nature. |
Monday, March 14, 2022 3:36PM - 3:48PM |
D64.00004: Lattice renormalization group approach to the quantum ordered states of the one-dimensional extended Hubbard model as a function of filling Lucas Desoppi, Nicolas Dupuis, Claude Bourbonnais One-dimensional interacting fermionic systems are usually studied in the continuum limit, with a spectrum linearized in the vicinity of the two Fermi points. In these approaches, lattice effects are mostly discarded, despite the fact that they may qualitatively affect the phase diagram of the models under study. We have developed a formalism based on the Fermionic Functional Renormalization Group for models defined on a lattice. One loop flow equations for the coupling constants and susceptibilities in the particle-particle and particle-hole channels have been derived. It is shown that lattice effects manifest themselves through the curvature of the spectrum, and through the dependence of the coupling constants on momenta. In this talk, we discuss the application of this method to the phase diagram of the one-dimensional extended Hubbard model as a function of filling. In particular, the fate of the Charge Bond Ordered Wave phase and the disappearance of Umklapp processes away from half-filling are investigated. |
Monday, March 14, 2022 3:48PM - 4:00PM |
D64.00005: Novel Approach to Unveil Quantum Phase Transitions Using Fidelity Map Mohamad Ali Marashli, Wing Chi YU, HO KIN TANG The study of quantum phases and quantum phase transitions (QPTs) has been one of the most active research areas in condensed matter physics. Identifying quantum phase transitions is key to understanding complex and novel properties in condensed matter such as unconventional superconductors and topological materials. Fidelity has been widely used to detect various types of QPTs in interacting many-body systems. However, several unconventional transitions remain difficult to identify with current methods. We propose a novel approach, i.e. the fidelity map, to detect QPTs with higher accuracy and sensitivity as compared to the conventional fidelity measures. Our scheme extends the fidelity concept from a single-dimensional to a multi-dimensional quantity and uses a meta-heuristic algorithm to search for the critical points that globally maximize the fidelity within each phase. The resulting "fidelity map" can capture a wide range of phase transitions accurately even in small and novel systems without prior knowledge, expanding the available toolset to study phase transitions in new quantum many-body systems. |
Monday, March 14, 2022 4:00PM - 4:12PM |
D64.00006: Exotic Thermal Transitions with Spontaneous Symmetry Breaking Hanbit Oh, Eun-Gook Moon We show that exotic thermal transitions with spontaneous symmetry breaking are hosted by thermal phases with topological orders. Our analysis is controlled by finding and perturbing the exact solutions of quantum rotor models coupled to the three-dimensional toric code. We evaluate all critical exponents and find striking characteristics of the exotic transitions. Remarkably, the Ising and XY transitions have the same universality class, and the exotic transitions are more stable than the Wilson-Fisher classes under couplings to acoustic phonons and Fermi surfaces. Thus, topological orders characterize thermal transitions with spontaneous symmetry breaking in sharp contrast to the conventional wisdom stating that order parameter symmetry and spatial dimension sorely determine the universality classes of thermal transitions. Applying our results to experiments in strongly correlated systems, we provide a plausible scenario in puzzlings of doped RbFe$_2$As$_2$. |
Monday, March 14, 2022 4:12PM - 4:24PM |
D64.00007: Steady-state solution for one-dimensional-open-quantum systems Tharnier P Oliveira, Stefano Chesi, Stefan Kirchner, Pedro Ribeiro The generalization of quantum phase transitions into non-equilibrium conditions raises several questions. In particular, how to classify the out-of-equilibrium critical phenomena into universality classes, in analogy with thermal equilibrium? |
Monday, March 14, 2022 4:24PM - 4:36PM |
D64.00008: Chiral symmetry breaking through spontaneous dimerization in kagom\'e metals Kitinan Pongsangangan, Riccardo Ciola, Ronny Thomale, Lars Fritz Due to an uprise in the variety of candidate compounds, kagome metals have recently gained significant attention. Among other features, kagome metals host Dirac cones as a key band structure feature away from half filling, and potentially yield an exceptionally large fine structure, beyond values found in other 2D Dirac materials such as graphene. We investigate the possibility of chiral symmetry breaking in kagome metals. Based on a heuristic lattice model, we determine the critical coupling strength and the ordering pattern by means of a Schwinger-Dyson mean-field analysis. As the leading instability we identify a dimerization pattern which spontaneously opens an excitation gap at the Dirac point and breaks the chiral symmetry. |
Monday, March 14, 2022 4:36PM - 4:48PM |
D64.00009: Ferroelectric quantum phase transitions and polar elasticity Dan Scott, Stephen E Rowley Ferroelectrics tuned to the neighbourhood of zero temperature phase transitions present an unexpected and novel form of criticality due to the quantum fluctuations of electrical dipole fields. For displacive materials crystalizing in three spatial dimensions with multiaxial order-parameters, these fluctuations appear to exist in an effective four-dimensional space leading to non-classical temperature dependences of the electrical susceptibility and thermal expansion. The coupling of the polarization and strain fields leads to a quantum polar-elastic regime characterized by a low-temperature peak in the susceptibility in paraelectrics near to ferroelectric quantum critical points. We present experimental and theoretical results of the electrical susceptibility and Grüneissen ratio and explore the phase diagram of KTaO3 and SrTiO3 using pressure and uniaxial stress tuning. At temperatures well below the peak, we discuss evidence for the emergence of a liquid of polarization textures exhibiting slow dynamics and a departure from the standard model of ferroelectric quantum criticality. An investigation of the insulating 'vacuum' state is likely to aid our understanding of forms of unconventional superconductivity as recently detected in electron-doped bulk and interface quantum ferroelectrics. |
Monday, March 14, 2022 4:48PM - 5:00PM |
D64.00010: Deconfined criticality and bosonization duality in easy-plane Chern-Simons two-dimensional antiferromagnets Vira Shyta Two-dimensional quantum systems with competing orders can feature a deconfined quantum critical point, yielding a continuous phase transition that is incompatible with the Landau-Ginzburg-Wilson (LGW) scenario, predicting instead a first-order phase transition. This is caused by the LGW order parameter breaking up into new elementary excitations at the critical point. Canonical candidates for deconfined quantum criticality are quantum antiferromagnets with competing magnetic orders, captured by the easy-plane CP1 model. A delicate issue however is that numerics indicate the easy-plane CP1 antiferromagnet to exhibit a first-order transition. We will explore the intricate critical behavior of this model through the particle-vortex duality and demonstrate an overlooked critical regime in the dual model. Furthermore, we will show that an additional topological Chern-Simons term in the action changes this picture completely in several ways. We will find that the topological easy-plane antiferromagnet undergoes a second-order transition with quantized critical exponents. Moreover, a particle-vortex duality naturally maps the partition function of the Chern-Simons easy-plane antiferromagnet into one of massless Dirac fermions. |
Monday, March 14, 2022 5:00PM - 5:12PM |
D64.00011: Non-Hermitian quantum gases: a platform for imaginary time crystals Rodrigo Arouca, Eduardo Cantera Marino, Cristiane Morais Smith One of the most important applications of quantum mechanics is the thermodynamic description of quantum gases. Despite the fundamental importance of this topic, a comprehensive description of the thermodynamic properties of non-Hermitian quantum gases is still lacking. Here, we investigate the properties of bosonic and fermionic non-Hermitian systems at finite temperatures. We show that non-Hermitian systems exhibit oscillations both in temperature and imaginary time. As such, they can be a possible platform to realize an imaginary time crystal (iTC) phase. The Hatano-Nelson model is identified as a simple lattice model to reveal this effect. In addition, we show that the conditions for the iTC to be manifest are the same as the conditions for the presence of disorder points, where the correlation functions show oscillating behavior. This analysis makes clear that our realization of iTC is effectively a way to filter one specific Matsubara mode. In this realization, the Matsubara frequency, which enters as a mathematical tool to compute correlation functions for finite temperatures, can be measured experimentally. |
Monday, March 14, 2022 5:12PM - 5:24PM |
D64.00012: Exploring a link between time crystals and many-body scars in long-range interacting systems Kieran Bull, Andrew Hallam, Zlatko Papic, Ivar Martin Time crystal is a non-equilibrium state of matter which spontaneously breaks time translation symmetry. While the existence of time crystals has been theoretically and experimentally established in periodically driven systems, resulting in a spontaneous breaking of a discrete $\mathbb{Z}_2$ symmetry, here we investigate the possibility of a \emph{continuous} time crystal, which has been proposed to occur in undriven, energy-conserving systems exhibiting prethermalization. Such systems are characterized by an exponentially long regime where thermalization is delayed, allowing the system to order and display long-lived oscillations of its order parameter, with the frequency set by the chemical potential. On the other hand, persistent oscillations have also recently been shown to arise due to a seemingly distinct mechanism of quantum many-body scarring: the emergence of a subspace of non-thermalizing eigenstates forming an su(2) algebra representation. In this paper we investigate a possible link between these two non-equilibrium phenomena in a realistic one-dimensional spin-1/2 model with long-range interactions. We identify a broad parameter regime with a weakly broken SU(2) symmetry, where the model hosts quantum many-body scars. On the other hand, our extensive numerical study did not find conclusive evidence of a time crystal phase, expected to arise for sufficiently long-range interactions. We relate the difficulty of observing a continuous time crystal to a lack of separation between the prethermalization and full thermalization time scales, found to be surprisingly insensitive to variation of the parameters of the model. |
Monday, March 14, 2022 5:24PM - 5:36PM |
D64.00013: Continuous transition between an ordered Ising magnet and a topological phase Shankar Ganesh, Chien-Hung Lin, Joseph Maciejko We propose a theory of phase transitions between symmetry breaking and (intrinsic) topological phases in two-dimensional Ising spin systems. This is done by means of a parton decomposition of the Ising spins into 2N Majorana fermions, which are assumed at the mean-field level to form a Class D topological superconductor with Chern number C. Various phases are obtained by tuning C. For example, transitions between C=0,1,2 phases are described by a parton theory of massive Majorana fields coupled to an internal SO(2N) gauge field with a Chern-Simons term. Utilising various level-rank dualities of Chern-Simons-matter theories, and instanton resummation methods originally developed by 't Hooft in the solution of the U(1) problem in QCD, we demonstrate phase transitions between paramagnetic, magnetically ordered, and quantum spin liquid phases for the physical Ising spins. |
Monday, March 14, 2022 5:36PM - 5:48PM |
D64.00014: Quantum criticality in La-doped CeIn Eundeok Mun, Suyoung Kim, Harim Jang, Soon-Gil Jung, Sangyun Lee, Soonbeom Seo, Sung-Il Kim, Cheol Kim, ChanKoo Park, Hanoh Lee, Tuson Park Applying pressure to CeIn3 suppresses the antiferromagnetic ordering (TN) to zero temperature and induces a magnetic to paramagnetic transition at a critical pressure 2.65 GPa. However, the nature of quantum criticality in CeIn3 is still under debate, where both conventional and unconventional critical states are observed from various physical property measurements. Here we report experiments of Ce1-xLaxIn3 system under pressure. The pressure evolution of TN in Ce1-xLaxIn3 series is similar to that of CeIn3. For 50% La substitution, TN of 4 K decreases with pressure and was completely suppressed at 1.31 GPa, where the non-fermi liquid behavior is observed. Interestingly, electrical resistivity and Hall coefficient measurements as a function of doping and pressure suggest that f-electrons in Ce1-xLaxIn3 are delocalized before the system reaches the quantum critical point (QCP). [1] In this talk, the origin of the local maximum in Hall coefficient and the itinerant character of f-electrons beyond the QCP will be discussed comparatively for pure and La-diluted CeIn3. |
Monday, March 14, 2022 5:48PM - 6:00PM |
D64.00015: Square lattice plaquette valence bond solid (pVBS) phase in SU(N) designer Hamiltonian with two-column representation Souvik Kundu, Nisheeta Desai, Kedar Damle We construct an SU(N) symmetric designer four-spin Hamiltonian with a two-column representation and find that it realizes a plaquette valence bond solid (pVBS) phase on the square lattice for N ≥ 3. We add to this interaction the SU(N) Heisenberg interaction with a two-column representation which is known to realize the Néel phase for N ≤ 9 and the Haldane Nematic phase otherwise. We study the phase diagram of this model as a function of the relative strengths of the two interactions as well as the value of N. We establish direct transitions from the Néel and Haldane Nematic phases into the pVBS phase on increasing the strength of the plaquette interaction for small and large N respectively. We determine the nature of the two transitions to be first order. |
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