Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session X07: Novel Approaches to Studying Quantum MatterFocus

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Sponsoring Units: DCMP Chair: Laurel Winter, Los Alamos National Laboratory Room: BCEC 109B 
Friday, March 8, 2019 8:00AM  8:12AM 
X07.00001: BosonFermion Duality in Four Dimensions Takuya Furusawa, Yusuke Nishida In this talk, we propose a novel bosonfermion duality in four spacetime dimensions by generalizing the lattice construction approach [1], which was applied to derive 3D bosonfermion duality [2]. Our analysis suggests that the Abelian Higgs model of θ=π is equivalent to a free Dirac fermion. The phase transition between topological and trivial insulators on the fermion side is dual to that between Higgs and confined phases on the boson side. Moreover, the Dirac fermion corresponds to a threebody bound state of one Higgs boson and two dyons in the bosonic theory. 
Friday, March 8, 2019 8:12AM  8:24AM 
X07.00002: Monte Carlo Study of Compact Quantum Electrodynamics at larger Fermion Flavors Wei Wang, Xiao Yan Xu, Chong Wang, Zi Yang Meng Based on our development in quantum Monte Carlo (QMC) technique (arXiv:1807.07574), the compact U(1) lattice gauge theory coupled to fermionic matter at (2+1)D is now accessible with largescale numerical simulations, and the phase diagram as a function of fermion flavor and the strength of gauge fluctuations is mapped out. Here we focus on the large fermion flavor case (Nf>=8), where the deconfineconfine phase transition is investigated in detail. In the deconfine phase, fermions coupled to the fluctuating gauge field to form U(1) spin liquid and in the confined phase, fermions are gapped out into valence bond solid. The different behaviors in terms of gauge flux, spectral of gaugeinvariant observables as well as the deconfineconfine phase transition (QED3GrossNeveutype) are presented. 
Friday, March 8, 2019 8:24AM  8:36AM 
X07.00003: Exact Results on Itinerant Ferromagnetism and the 15puzzle Problem Eric Bobrow, Keaton Stubis, Yi Li We apply a result from graph theory to prove exact results about itinerant ferromagnetism. Nagaoka's theorem of ferromagnetism is extended to all nonseparable graphs except single polygons with more than four vertices by applying the solution to the generalized 15puzzle problem, which studies whether the hole's motion can connect all possible tile configurations. This proves that the ground state of a U→∞ Hubbard model with one hole away from the half filling on a 2D honeycomb lattice or a 3D diamond lattice is fully spinpolarized. Furthermore, the condition of connectivity for Ncomponent fermions is presented, and Nagaoka's theorem is also generalized to SU(N)symmetric fermion systems on nonseparable graphs. 
Friday, March 8, 2019 8:36AM  8:48AM 
X07.00004: The Fermion Bag Approach to Hamiltonian Theories Emilie Huffman, Shailesh Chandrasekharan Quantum Monte Carlo (QMC) methods, when applicable, offer dependable ways to extract the nonperturbative physics of stronglycorrelated manybody systems. However, there are some formidable bottlenecks to the applicability of these methods such as the sign problem and algorithmic update inefficiencies. Using the tV model Hamiltonian, we demonstrate how the fermion bag approachoriginally developed in the context of Lagrangian lattice field theoriesled to the first sign problem solution for this model. We then show how using fermion bag ideas to develop a new efficient QMC algorithm to study the tV model allowed us to compute critical exponents for the chiral Ising universality class (involving one flavor of fourcomponent Dirac fermions) that seem to be more reliable than those from previous QMC calculations. Finally, we discuss how the fermion bag approach offers certain advantages to the study of other models involving Dirac fermions and also extends to fermionspin interactions and Z_2 gauge theories. 
Friday, March 8, 2019 8:48AM  9:00AM 
X07.00005: Fracton and Holography Han Yan We propose that the fracton topological order is a class of toy models for holography. The discovery of AdS/CFT correspondence as a concrete construction of holography, and the subsequent developments including the RyuTakayanagi formula of entanglement entropy have revolutionized our understanding of quantum gravity, and provided a powerful tool set for solving various stronglycoupled quantum field theory problems. In this work we discuss a classical toy model based on fracton topological order, a class of exotic manybody systems with boundary area law of ground state degeneracy and (partially) immobile excitations. We show that such a model defined on the hyperbolic lattice satisfies some key properties of holographic correspondence. These properties include: the AdSRindler reconstruction is realized; the mutual information obeys the RyuTakayanagi formula, and a naively defined black hole's entropy scales as its horizon area. 
Friday, March 8, 2019 9:00AM  9:12AM 
X07.00006: Monte Carlo Study of Compact Quantum Electrodynamics with Fermionic Matter: the Parent State of Quantum Phases Yang Qi, Xiao Yan Xu, Long Zhang, Fakher Assaad, Cenke Xu, Zi Yang Meng The interplay between lattice gauge theories and fermionic matter accounts for fundamental physical phenomena ranging from the deconfinement of quarks in particle physics to quantum spin liquid with fractionalized anyons and emergent gauge structures in condensed matter physics. Here we show that the problem of compact U(1) lattice gauge theory coupled to fermionic matter in (2+1)D is possible to access via signproblemfree quantum Monte Carlo simulations. One can hence map out the phase diagram as a function of fermion flavors and the strength of gauge fluctuations. By increasing the coupling constant of the gauge field, gauge confinement in the form of various spontaneous symmetry breaking phases such as valence bond solid (VBS) and Néel antiferromagnet emerge. Deconfined phases with algebraic spin and VBS correlation functions are also observed. Such deconfined phases are an incarnation of exotic states of matter, i.e. the algebraic spin liquid, which is generally viewed as the parent state of various quantum phases. The phase transitions between deconfined and confined phases, as well as that between the different confined phases provide various manifestations of deconfined quantum criticality. 
Friday, March 8, 2019 9:12AM  9:24AM 
X07.00007: Hidden SU(2) Symmetries, Symmetry Hierarchy and Emergent EightFoldWay in Spin1 Quantum Magnets HuiKe Jin, Yi Zhou, JianJian Miao The allowed largest symmetry in quantum spin1 systems is SU(3) rather than spin rotational SO(3). In this work, we study some SU(2) symmetries as subgroups of the SU(3), which was not bewared in literature to the best of our knowledge. We construct twobody Hamiltonians where these SU(2) symmetries are respected, and explore the ground phase diagram according to the symmetry hierarchy SU(3)/SU(2)×U(1). It is natural to treat the eight generators of the SU(3) symmetry on an equal footing, called eightfoldway. And possible experimental consequences are discussed as well. 
Friday, March 8, 2019 9:24AM  9:36AM 
X07.00008: Numerically study the conformality of Qstate 1+1D quantum Potts model at Q>4 Han Ma, YinChen He The existence of complex conformal field theory (CFT) is proposed to be a mechanism of weak first order phase transition featuring extremely slow renormalization group flow with approximate scale invariance. We numerically study the simplest platform of this physics — the Qstate 2D Potts model when Q>4. We find that the properties of the phase transition are well captured by the complex CFTs. The central charge and conformal tower are extracted and studied. We also analyze how these data rely on length scale using conformal perturbation theory away from the nearby complex CFT. 
Friday, March 8, 2019 9:36AM  9:48AM 
X07.00009: Slow scrambling in a quantum rotor model with random exchange interactions Dan Mao, Debanjan Chowdhury, Senthil Todadri In recent years, outoftimeorder correlation functions (OTOC) have been used to diagnose the onset of information scrambling in a wide class of problems, ranging from black holes to interacting field theories and lattice models. We study the OTOC for a solvable model of a large number (N) of Mcomponent quantum rotors coupled by Gaussiandistributed random, infiniterange exchange interactions [1]. At a finite temperature above the quantum critical point separating a spinglass and a paramagnetic phase, there is no exponential growth of the OTOC of the rotor fields. We show that in this large N, M limit, the random rotor model is integrable, and can be described by random matrix theory. The apparent lack of quasiparticle excitations in this limit arises as a result of disorder averaging and not strong interactions. We also compute the leading 1/M contribution to the OTOC of the rotor fields and find a slow exponential growth. 
Friday, March 8, 2019 9:48AM  10:00AM 
X07.00010: Superfluidity without Condensation Anthony Hegg, Wei Ku The connection between superfluidity and BoseEinstein condensation (BEC) is well studied in 3D, but it is untenable in 2D due to the lack of condensation in such systems. We develop a new microscopic theory that exhibits low temperature superfluidity on a 2D lattice despite the lack of condensation and show that it has surprising properties. Fluctuations play a key role in the stability of this superfluid, and it is more robust than superfluidity in the presence of a BEC. Finally, we discuss the application of this mechanism to produce superfluidity in a 3D system. 
Friday, March 8, 2019 10:00AM  10:12AM 
X07.00011: Numerically efficient parquetequations solver for correlated electron systems Christian Eckhardt, Anna Kauch, Giulio A.H. Schober, Carsten Honerkamp, Karsten Held The parquet equations are a set of selfconsistent equations for the effective 

X07.00012: ABSTRACT WITHDRAWN

Friday, March 8, 2019 10:24AM  10:36AM 
X07.00013: Fibonacci Topological Superconductor Yichen Hu, Charles Kane In this talk we will present a model of interacting Majorana fermions that describes a superconducting phase with a topological order characterized by the Fibonacci topological field theory. Our theory, which is based on a SO(7)_{1}/(G_{2})_{1} coset factorization, leads to a solvable one dimensional model without parafermions that is extended to two dimensions using a network construction. In addition, we predict a closely related "antiFibonacci" phase, whose topological order is characterized by the tricritical Ising model. We will show that Majorana fermions can split into a pair of Fibonacci anyons, and propose an interferometer that generalizes the Z_{2} Majorana interferometer and directly probes the Fibonacci nonAbelian statistics. 
Friday, March 8, 2019 10:36AM  10:48AM 
X07.00014: Nonlocal probes for stronglycorrelated quantum phases Barbara CapogrossoSansone, Fabio Lingua, Wei Wang, Liana Shpani In this talk, we propose nonlocal probes to study correlations in lattice bosons. We argue that these probes can be used as an alternative to characterize quantum phases. We use PathIntegral MonteCarlo and define the proposed probes in terms of the geometric braiding in worldline configurations. We show that these probes can be used as alternatives to local orderparameters in certain known phase transitions. Further, we describe a framework which links these probes (based on braiding properties of in worldline configurations) to entanglement in hardcore lattice bosons. 
Friday, March 8, 2019 10:48AM  11:00AM 
X07.00015: Effective spinorbit models using correlated firstprinciples wave functions Yueqing Chang, Lucas Wagner In recent years, spinorbit effects have been used to design and predict new emergent phases in condensed matter systems. Most of the theory has been done at the level of band structure. It is of high current interest how to extend these ideas to correlated electron systems. We present a new computational technique that uses firstprinciples quantum Monte Carlo calculations to address spinorbit effects efficiently while also treating electron correlation accurately. To test this technique, we perform benchmark calculations in atomic systems and monolayer tungsten disulfide. The calculated results of the spinorbit splittings in these systems agree with the experimentally determined values. This new tool allows us to investigate electronelectron interaction, spinorbit effects and onebody terms on the same footing in realistic materials, with a cost similar to the standard fixednode diffusion Monte Carlo. 
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