Arxiv Selection Mar 2019

Mar 1-Mar 7 Zehan Li, Mar 8-Mar 14 Jiansong Pan, Mar 15-Mar 21 Ahmet Keles, Mar 22- Mar 28 Haiping Hu

Mar 1

arXiv:1902.06584 (cross-list from cond-mat.str-el) [pdf, ps, other]

Bosonization with background U(1) gauge field

Yuan Yao, Yoshiki Fukusumi

Comments: 9 pages, 8 figures

Subjects: Strongly Correlated Electrons (cond-mat.str-el); Quantum Gases (cond-mat.quant-gas); Statistical Mechanics (cond-mat.stat-mech); High Energy Physics - Theory (hep-th); Mathematical Physics (math-ph)

Bosonization is one of the most significant frameworks to analyze fermionic systems. In this work, we propose a new bosonization of Dirac fermion coupled with U(1) background gauge field consistent with gauge invariance, global chiral anomaly matching and fermion-boson operator correspondence, either of which is not satisfied by previously developed bosonizations. The bilinear Dirac-mass term condensation paradox and its generalized form are resolved by our bosonization. This new bosonization approach to interacting systems also correctly captures the conformal characters of a significant class of critical lattice models, such as conformal dimensions and conformal anomaly of XXZ spin chain with twisted boundary condition. Our work clarifies the equivalence of fermionic flux insertion and bosonic background charge insertion for two-dimensional conformal field theory

Mar 2

arXiv:1902.09747 [pdf, ps, other]

Imaginary time crystal of quantum gases

Zi Cai, Yizhen huang, W. Vincent Liu

Subjects: Quantum Gases (cond-mat.quant-gas)

Floquet or discrete time crystal was predicted as a form of super-crystallization from the “periodic” time lattice of varying Hamiltonians. Subsequent experiments of trapped ions and nitrogen-vacancy centers discovered it. However, whether such a phase can emerge from time continuum, as originally introduced, remains an open question because of the no-go theorem on quantum mechanical ground state. Here we report that by relaxing the scope to open quantum systems, time crystalline ordering can emerge spontaneously by breaking continuous translational symmetry in imaginary time dual space due to retarded interaction induced by thermal bath. Quantum Monte Carlo simulation is performed to calculate a time order parameter and previously unknown “time” excitation response functions from the Euclidean action.

Mar 5

arXiv:1902.10792 [pdf, other]

Anomalous phase ordering of a quenched ferromagnetic superfluid

L. A. Williamson, P. B. Blakie

Subjects: Quantum Gases (cond-mat.quant-gas)

Coarsening dynamics, the canonical theory of phase ordering following a quench across a symmetry breaking phase transition, is thought to be driven by the annihilation of topological defects. Here we show that this understanding is incomplete. We simulate the dynamics of an isolated spin-1 condensate quenched into the easy-plane ferromagnetic phase and find that the mutual annihilation of spin vortices does not take the system to the equilibrium state. A nonequilibrium background of long wavelength spin waves remain at the BerezinskiiKosterlitz-Thouless temperature, an order of magnitude hotter than the equilibrium temperature. The coarsening continues through a second much slower scale invariant process with a length scale that grows with time as t 1/3 . This second regime of coarsening is associated with a turbulent cascade that transports spin wave energy from low to high wavevectors, bringing about the the eventual equilibrium state. Because the relevant spin-waves are noninteracting, the cascade occurs through a dynamic coupling to other degrees of freedom of the system. Strongly coupling the system to a reservoir destroys the second regime of coarsening, allowing the system to thermalise following the annihilation of vortices. Our results, which provide a connection between the currently disparate fields of phase ordering dynamics and wave turbulence, offer a paradigm for understanding phase ordering dynamics beyond the current framework built around topological defects.