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arXiv · 1705.11047

Phase Transitions in $Z_{n}$ Gauge Models: Towards Quantum Simulations of the Schwinger-Weyl QED

Elisa Ercolessi·Paolo Facchi·Giuseppe Magnifico·Saverio Pascazio·Francesco V. Pepe
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Abstract

We study the ground-state properties of a class of $\mathbb{Z}_n$ lattice gauge theories in 1 + 1 dimensions, in which the gauge fields are coupled to spinless fermionic matter. These models, stemming from discrete representations of the Weyl commutator for the $\mathrm{U}(1)$ group, preserve the unitary character of the minimal coupling, and have therefore the property of formally approximating lattice quantum electrodynamics in one spatial dimension in the large-$n$ limit. The numerical study of such approximated theories is important to determine their effectiveness in reproducing the main features and phenomenology of the target theory, in view of implementations of cold-atom quantum simulators of QED. In this paper we study the cases $n = 2 ÷8$ by means of a DMRG code that exactly implements Gauss' law. We perform a careful scaling analysis, and show that, in absence of a background field, all $\mathbb{Z}_n$ models exhibit a phase transition which falls in the Ising universality class, with spontaneous symmetry breaking of the $CP$ symmetry. We then perform the large-$n$ limit and find that the asymptotic values of the critical parameters approach the ones obtained for the known phase transition the zero-charge sector of the massive Schwinger model, which occurs at negative mass.

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Elisa Ercolessi, Paolo Facchi, Giuseppe Magnifico, Saverio Pascazio, Francesco V. Pepe. 2018-10-05. Phase Transitions in $Z_{n}$ Gauge Models: Towards Quantum Simulations of the Schwinger-Weyl QED. https://doi.org/10.1103/physrevd.98.074503

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