Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session X44: Quantum Phase Transition TheoryLive

Hide Abstracts 
Sponsoring Units: DCMP Chair: Emilian Nica, Arizona State University 
Friday, March 19, 2021 8:00AM  8:12AM Live 
X44.00001: Multifixed point numerical conformal bootstrap: a case study with structured global symmetry Matt Dowens, Christopher A Hooley The numerical conformal bootstrap offers the possibility of finding and classifying conformal field theories of quantum critical systems in 2+1 dimensions, and thus obtaining nonperturbative information about their phase diagrams. However, its future utility depends on its ability to accurately predict the existence of hitherto unknown nontrivial conformal field theories (CFTs). Here we investigate the extent to which this is possible in the case where the global symmetry group has a product structure. 
Friday, March 19, 2021 8:12AM  8:24AM Live 
X44.00002: Order, Disorder, and Transitions in AKLTlike States on the Decorated Bethe Lattice Nicholas Pomata We consider the AKLT state on the Bethe lattice (solved by Affleck, Kennedy, Lieb, and Tasaki in 1988 and Fannes, Nachtergaele, and Werner in 1991), and extend it, first to a variant with a chain of n spin1 decorations on each edge. Having found the recurrence relations that define their longrange behavior in each case, we use two continuouslyparametrized variants of those decorations to interpolate between those cases. In those systems we are able to find orderdisorder transitions on Bethe lattices of any coordination number z>4. We analyze these critical points exactly, finding simple critical exponents. 
Friday, March 19, 2021 8:24AM  8:36AM Live 
X44.00003: Order by disorder in a quantum annealer Sumner Hearth, Siddhardh C Morampudi, Christopher Laumann Quantum annealers offer the possibility of simulating theoretical phenomena in ideal models which are tricky to observe in typical settings due to complications such as disorder and temperature. One such example is quantum order by disorder where quantum fluctuations can generate an ordered state in frustrated systems at very low temperatures. We show the appearance of a quasiordered phase in the squareoctagon fully frustrated transverse field Ising model generated through quantum order by disorder in a quantum annealer of 996 qubits. The results are benchmarked against theoretical tools such as Landau theory and also quantum Monte Carlo simulations. 
Friday, March 19, 2021 8:36AM  8:48AM Live 
X44.00004: Quantum critical behavior of the GrossNeveuSO(3) universality class: 4−ε expansion, 1/N expansion, and functional renormalization group Shouryya Ray, Bernhard Ihrig, Michael M Scherer, John A Gracey, Lukas Janssen The GrossNeveuSO(3) universality class describes a quantum critical point between a Dirac semimetal and a phase with longrange order, in which the fermion spectrum is only partially gapped out. Such a quantum critical point has recently been predicted to be realizable in twodimensional spinorbital magnets with strong exchange frustration. In this talk, I shall report on our work characterizing the quantum critical behavior of the GrossNeveuSO(3) universality class from three complementary fieldtheoretical approaches: threeloop ε expansion around the upper critical spacetime dimension of four, secondorder largeN expansion (partly even at third order), as well as functional renormalization group in the local potential approximation. 
Friday, March 19, 2021 8:48AM  9:00AM Live 
X44.00005: Confinement transition in the QED_{3}GrossNeveuXY universality class Lukas Janssen, Wei Wang, Michael M Scherer, Zi Yang Meng, Xiao Yan Xu The coupling between fermionic matter and gauge fields plays a fundamental role in our understanding of nature, while at the same time posing a challenging problem for theoretical modeling. In this situation, controlled information can be gained by combining different complementary approaches. In this talk, I will discuss a confinement transition in a system of N_{f} flavors of interacting Dirac fermions charged under a U(1) gauge field in 2+1 dimensions. Using Quantum Monte Carlo simulations, we investigate a lattice model that exhibits a continuous transition at zero temperature between a gapless deconfined phase, described by threedimensional quantum electrodynamics, and a gapped confined phase, in which the system develops valencebondsolid order. We argue that the quantum critical point is in the universality class of the QED_{3}GrossNeveuXY model. We study this field theory within a 1/N_{f} expansion in fixed dimension as well as a renormalization group analysis in 4−ε spacetime dimensions. The consistency between numerical and analytical results is revealed from large to intermediate flavor number. 
Friday, March 19, 2021 9:00AM  9:12AM Live 
X44.00006: Duality Protected MultiCriticality in Deconfined Quantum Phase Transitions Dachuan Lu, Yizhuang You Duality places an important constraint on the renormalization group flows and the phase diagrams. For selfdual theories, the duality can be promoted as a symmetry, this leads to the multicriticalities. For example, the deconfined quantum critical point has selfdual descriptions. This work investigates the multicritical behavior of this kind of theory under perturbative deformation. To be specific, the QED3 with the ChernSimons term is used to describe such quantum phase transitions, and the GrossNeveu term is introduced to describe the multicriticality. By doing the largeN renormalization group analysis, we find the multicriticality falls in different universality classes from the corresponding nearby continuous transitions. Scaling dimensions of the possible nonrelativistic 4fermion interactions are calculated, these operators have their counterparts in the lattice models. Specifically, our calculation shows certain spinspin interactions will drive the deconfined quantum criticality to first order as found in previous numerical studies. 
Friday, March 19, 2021 9:12AM  9:24AM Live 
X44.00007: ab initio Gutzwiller quantum molecular dynamics simulation of hydrogens under extreme conditions Chen Cheng, Giawei Chern Molecular dynamics (MD), a computer simulation method for studying the dynamical evolution of molecules and atoms, has achieved great success in the past decades and has been widely used in a variety of research fields. In particular, the ab initio molecular dynamics (AIMD) methods, in which the electron degrees of freedom are integrated out on the fly from first principles, have become the stateoftheart tool for accurate modeling of physical phenomena and functional materials. In most AIMD simulations, the electronic structure problem is solved using the density functional theory (DFT). However, it is known that DFT fails to capture effects of strong electron correlation. To overcome this obstacle, here we present a novel AIMD scheme based on the Gutzwiller/slaveboson manybody technique, which has been shown to successfully describe the correlationinduced metalinsulator transitions. We applied our ab initio Gutzwiller MD to simulate the dissociation of hydrogen molecules in the highpressure liquid phase. Our work sheds new light on the role of electron correlation in this intriguing liquidliquid transition of hydrogens. 
Friday, March 19, 2021 9:24AM  9:36AM Live 
X44.00008: Symmetry Breaking Effects of Instantons in Parton Gauge Theories Shankar Ganesh, Joseph Maciejko Transitions between fractionalized and conventional quantum phases of matter in 2+1 dimensions are conceptually best understood within the framework of parton gauge theories, whereby the confinement of fractionalized excitations and spontaneous breaking of global symmetries in conventional phases is argued to result from the proliferation of gauge monopoles/instantons. To complement recent studies of the quantum numbers and scaling dimensions of monopole operators in parton gauge theories of frustrated quantum antiferromagnets, we provide an explicit semiclassical derivation of instanton contributions to the lowenergy effective parton gauge theory for hardcore bosons on the honeycomb lattice using methods originally developed by 't Hooft in the solution of the U(1) problem in quantum chromodynamics. While the symmetrybreaking effect of instantons is typically associated with massless fermions and the AtiyahSinger index theorem on compact manifolds, we show that the spontaneous breaking of the U(1) boson number conservation symmetry in the superfluid phase results here from Euclidean zero modes of massive Dirac fermions bound to instantons in noncompact spacetime. 
Friday, March 19, 2021 9:36AM  9:48AM Live 
X44.00009: Continuous phase transitions in diagrammatic Monte Carlo Connor Lenihan, Aaram J. Kim, Fedor Simkovic, Evgeny Kozik In the diagrammatic Monte Carlo approach, properties of a strongly correlated system are represented by the series of Feynman diagrams in the thermodynamic limit. We demonstrate that the location of a continuous phase transition can be found from the series coefficients for diverging susceptibility in the normal state. We obtain the coefficients to high order such that they contain sufficient information to locate the transition by using the known critical behaviour, for a given universality class, to extract the location of the singularity in an accurate way. We demonstrate this by mapping the Néel transition of the 3d Hubbard model across a range of dopings and temperatures. 
Friday, March 19, 2021 9:48AM  10:00AM Live 
X44.00010: Instanton Crystal Phase Grigorii Starkov, Konstantin Efetov We propose a class of models exhibiting instanton crystal phase. In this 
Friday, March 19, 2021 10:00AM  10:12AM Live 
X44.00011: Attractive Effect of a Strong Electronic Repulsion: The Physics of Vertex Divergences Lorenzo Del Re, Matthias Reitner, Patrick Chalupa, Daniel Springer, Sergio Ciuchi, Giorgio Sangiovanni, Alessandro Toschi While the breakdown of the perturbation expansion for the manyelectron problem has several formal consequences, here we unveil its physical effect: flipping the sign of the effective electronic interaction in specific scattering channels. By decomposing local and uniform susceptibilities of the Hubbard model via their spectral representations, we prove how entering the nonperturbative regime causes an enhancement of the charge response, ultimately responsible for the phaseseparation instabilities close to the Mott metalinsulator transition. Our analysis opens a new route for understanding phase transitions in the nonperturbative regime and clarifies why attractive effects emerging from a strong repulsion can induce phase separations but not swave pairing or chargedensity wave instabilities. 
Friday, March 19, 2021 10:12AM  10:24AM Live 
X44.00012: Stability of the unconventional $\mathbb{Z}_{n}$ parton states at $\nu = 7/3$:
The role of finite width William Faugno, Tongzhou Zhao, Ajit Coimbatore Balram, Thierry Jolicoeur, Jainendra Jain A class of $\mathbb{Z}_n$ parton states has been proposed for the onethird filled second Landau level. These represent superconductivity of bound states of n composite bosons, and support excitations with fractional charge $e/3n$. We consider the feasibility of these states at onethird filled second Landau level as a function of the semiconductor quantum well. We find a phase transition as a function of quantum well width where a parton state is favored for small well widths and the Laughlin state is stabilized beyond a critical well width. We also propose that a $\mathbb{Z}_n$ parton state is relevant at 1/3 filling in bilayer graphene at low magnetic fields. We discuss the role of spin and Landau level mixing, and also possible experimental signatures to distinguish $\mathbb{Z}_n$ parton states from Laughlin’s. 
Friday, March 19, 2021 10:24AM  10:36AM Live 
X44.00013: Universal tripartite entanglement in manybody systems Yijian Zou, Karthik Siva, Tomohiro Soejima, Roger Mong, Michael Zaletel Motivated by conjectures in holography relating the entanglement of purification and reflected entropy to the entanglement wedge crosssection, we introduce two related nonnegative measures of tripartite entanglement g and h. We prove structure theorems which show that states with nonzero g or h have nontrivial tripartite entanglement. We then establish that in 1D these tripartite entanglement measures are universal quantities that depend only on the emergent lowenergy theory. For a gapped system, we show that either g is positive and h=0 or both are zero, depending on whether the ground state has longrange order. For a critical system, we develop a novel numerical algorithm to compute g and h from lattice models. We compute g and h for various CFTs and show that h depends only on the central charge whereas g depends on the whole operator content. Finally, we discuss the implications of our results for holography. 
Friday, March 19, 2021 10:36AM  10:48AM Live 
X44.00014: Origin of the ν= 1/2 fractional quantum Hall effect in wide quantum wells Tongzhou Zhao, William Faugno, Songyang Pu, Jainendra Jain Previous studies have investigated the nature of the fractional quantum Hall effect at $\nu=1/2$ observed in wide quantum wells by the variational Monte Carlo method, which makes the assumption that the transverse wave function and the gap between the symmetric and antisymmetric subbands obtained in a local density approximation at zero magnetic field remain valid even at high perpendicular magnetic fields; this method also ignores the effect of Landau level mixing. We develop a threedimensional fixed phase diffusion Monte Carlo(DMC) method, which gives, in a single framework, the total energies of various candidate states in a finite width quantum well, including Landau level mixing, directly in a large magnetic field. This method can be applied to onecomponent states, as well twocomponent states in the limit where the symmetric and antisymmetric bands are nearly degenerate. Our threedimensional fixedphase DMC calculations suggest that the observed 1/2 fractional quantum Hall state in wide quantum wells is likely to be the onecomponent Pfaffian state supporting nonAbelian excitations. We also study the influence of the asymmetry of the quantum well on the ground states. 
Friday, March 19, 2021 10:48AM  11:00AM On Demand 
X44.00015: Continuous phase transition between Neel and valence bond solid phases on a spin ladder system Takuhiro Ogino, Ryui Kaneko, Satoshi Morita, Shunsuke Furukawa, Naoki Kawashima We investigate a quantum phase transition between a Neel phase and a valence bond solid (VBS) phase in the JQlike model in one spatial dimension. 
Follow Us 
Engage
Become an APS Member 
My APS
Renew Membership 
Information for 
About APSThe American Physical Society (APS) is a nonprofit membership organization working to advance the knowledge of physics. 
© 2023 American Physical Society
 All rights reserved  Terms of Use
 Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 207403844
(301) 2093200
Editorial Office
1 Research Road, Ridge, NY 119612701
(631) 5914000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 200452001
(202) 6628700