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Clock model interpolation and symmetry breaking in O(2) models
Journal article   Open access   Peer reviewed

Clock model interpolation and symmetry breaking in O(2) models

Leon Hostetler, Jin Zhang, Ryo Sakai, Judah Unmuth-Yockey, Alexei Bazavov and Yannick Meurice
Physical review. D, Vol.104(5), p.1
09/01/2021
DOI: 10.1103/PhysRevD.104.054505
url
https://doi.org/10.1103/PhysRevD.104.054505View
Published (Version of record) Open Access

Abstract

Motivated by recent attempts to quantum simulate lattice models with continuous Abelian symmetries using discrete approximations, we define an extended-O(2) model by adding a. cosoqfTHORN term to the ordinary O(2) model with angular values restricted to a 2p interval. In the.. 8 limit, the model becomes an extended q-state clock model that reduces to the ordinary q-state clock model when q is an integer and otherwise is a continuation of the clock model for noninteger q. By shifting the 2p integration interval, the number of angles selected can change discontinuously and two cases need to be considered. What we call case 1 has one more angle than what we call case 2. We investigate this class of clock models in two spacetime dimensions using Monte Carlo and tensor renormalization group methods. Both the specific heat and the magnetic susceptibility show a double-peak structure for fractional q. In case 1, the small-beta peak is associated with a crossover, and the large-beta peak is associated with an Ising critical point, while both peaks are crossovers in case 2. When q is close to an integer by an amount.q and the system is close to the small beta Berezinskii-Kosterlitz-Thouless transition, the system has a magnetic susceptibility that scales as similar to 1=o.q(+)1-1=d0 with d0 estimates consistent with the magnetic critical exponent d = 15. The crossover peak and the Ising critical point move to Berezinskii-Kosterlitz-Thouless transition points with the same powerlaw scaling. A phase diagram for this model in the o beta; q(+) plane is sketched. These results are possibly relevant for configurable Rydberg-atom arrays where the interpolations among phases with discrete symmetries can be achieved by varying continuously the distances among atoms and the detuning frequency.
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