Controlling Symmetries and Quantum Criticality in the Anisotropic Coupled-Top Model

• URL: http://arxiv.org/abs/2502.09394v1
• Date: Thu, 13 Feb 2025 15:14:29 GMT
• Title: Controlling Symmetries and Quantum Criticality in the Anisotropic Coupled-Top Model
• Authors: Wen-Jian Mao, Tian Ye, Liwei Duan, Yan-Zhi Wang,
• Abstract summary: We investigate the anisotropic coupled-top model, which describes the interactions between two large spins along both $x-$ and $y-$directions. We can manipulate the system's symmetry, inducing either discrete $Z$ or continuous U(1) symmetry. The framework provides an ideal platform for experimentally controlling symmetries and investigating associated physical phenomena.
• Score: 32.553027955412986
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• Abstract: We investigate the anisotropic coupled-top model, which describes the interactions between two large spins along both $x-$ and $y-$directions. By tuning anisotropic coupling strengths along distinct directions, we can manipulate the system's symmetry, inducing either discrete $Z_2$ or continuous U(1) symmetry. In the thermodynamic limit, the mean-field phase diagram is divided into five phases: the disordered paramagnetic phase, the ordered ferromagnetic or antiferromagnetic phases with symmetry breaking along either $x-$ or $y-$direction. This results in a double degeneracy of the spin projections along the principal direction for $Z_2$ symmetry breaking. When U(1) symmetry is broken, infinite degeneracy associated with the Goldstone mode emerges. Beyond the mean-field ansatz, at the critical points, the energy gap closes, and both quantum fluctuations and entanglement entropy diverge, signaling the onset of second-order quantum phase transitions. These critical behaviors consistently support the universality class of $Z_2$ symmetry. Contrarily, when U(1) symmetry is broken, the energy gap vanishes beyond the critical points, yielding a novel exponent of 1, rather than 1/2 for $Z_2$ symmetry breaking. The framework provides an ideal platform for experimentally controlling symmetries and investigating associated physical phenomena.

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