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arXiv · 2412.17605

Deconfined classical criticality in the anisotropic quantum spin-$\frac{1}{2}$ XY model on the square lattice

Christopher Mudry·Ömer M. Aksoy·Claudio Chamon·Akira Furusaki
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Abstract

The anisotropic quantum spin-1/2 XY model on a linear chain was solved by Lieb, Schultz, and Mattis in 1961 and shown to display a continuous quantum phase transition at the O(2) symmetric point separating two gapped phases with competing Ising long-range order. For the square lattice, the following is known. The two competing Ising ordered phases extend to finite temperatures, up to a boundary where a transition to the paramagnetic phase occurs, and meet at the O(2) symmetric critical line along the temperature axis that ends at a tricritical point at the Berezinskii-Kosterlitz-Thouless transition temperature where the two competing phases meet the paramagnetic phase. We show that the first-order zero-temperature (quantum) phase transition that separates the competing phases as a function of the anisotropy parameter is smoothed by thermal fluctuations into deconfined classical criticality.

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Christopher Mudry, Ömer M. Aksoy, Claudio Chamon, Akira Furusaki. 2024-12-23. Deconfined classical criticality in the anisotropic quantum spin-$\frac{1}{2}$ XY model on the square lattice. https://doi.org/10.1103/physrevb.111.104402

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