Emergent Intermediate Phase in the $J_1$-$J_2$ XY model from Tensor Network Approaches

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Main Authors: Song, Feng-Feng, Nuomin, Hanggai, Kawashima, Naoki
Format: Preprint
Published: 2024
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author Song, Feng-Feng
Nuomin, Hanggai
Kawashima, Naoki
author_facet Song, Feng-Feng
Nuomin, Hanggai
Kawashima, Naoki
contents We investigate the finite-temperature phase diagram of the classical $J_1$-$J_2$ XY model on a square lattice using a tensor network approach designed for frustrated spin systems. This model, characterized by competing nearest-neighbor and next-to-nearest-neighbor interactions, exhibits a complex interplay between $U(1)$ and $Z_2$ symmetries. Our study reveals an emergent intermediate phase around $J_2/J_1 \sim 0.505$, which is characterized by a $Z_2$ long-range stripe order without phase coherence in the XY spins. The intermediate phase features two well-separated phase transitions: a higher-temperature Ising transition and a lower-temperature Berezinskii-Kosterlitz-Thouless transition. The relative separation between these transitions is significantly larger than previously reported, enabling a clearer investigation of their distinct thermodynamic properties. For $0.5<J_2/J_1 < 0.501$, two transitions merge into a single first-order phase transition, a phenomenon that cannot be explained solely by mapping to the Ising-XY model. As $J_2/J_1 \to \infty$, the transition evolves continuously into the BKT universality class. These findings advance the understanding of the mechanisms driving phase transitions in frustrated spin systems and suggest potential experimental realizations in platforms such as ultracold atoms, Josephson junction arrays, and optical lattices.
format Preprint
id arxiv_https___arxiv_org_abs_2412_18892
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Emergent Intermediate Phase in the $J_1$-$J_2$ XY model from Tensor Network Approaches
Song, Feng-Feng
Nuomin, Hanggai
Kawashima, Naoki
Strongly Correlated Electrons
Statistical Mechanics
Superconductivity
We investigate the finite-temperature phase diagram of the classical $J_1$-$J_2$ XY model on a square lattice using a tensor network approach designed for frustrated spin systems. This model, characterized by competing nearest-neighbor and next-to-nearest-neighbor interactions, exhibits a complex interplay between $U(1)$ and $Z_2$ symmetries. Our study reveals an emergent intermediate phase around $J_2/J_1 \sim 0.505$, which is characterized by a $Z_2$ long-range stripe order without phase coherence in the XY spins. The intermediate phase features two well-separated phase transitions: a higher-temperature Ising transition and a lower-temperature Berezinskii-Kosterlitz-Thouless transition. The relative separation between these transitions is significantly larger than previously reported, enabling a clearer investigation of their distinct thermodynamic properties. For $0.5<J_2/J_1 < 0.501$, two transitions merge into a single first-order phase transition, a phenomenon that cannot be explained solely by mapping to the Ising-XY model. As $J_2/J_1 \to \infty$, the transition evolves continuously into the BKT universality class. These findings advance the understanding of the mechanisms driving phase transitions in frustrated spin systems and suggest potential experimental realizations in platforms such as ultracold atoms, Josephson junction arrays, and optical lattices.
title Emergent Intermediate Phase in the $J_1$-$J_2$ XY model from Tensor Network Approaches
topic Strongly Correlated Electrons
Statistical Mechanics
Superconductivity
url https://arxiv.org/abs/2412.18892