Year: 2025
Type: article
Abstract: The introduction of an asymmetric term into the quantum Rabi model generally lifts energy-level degeneracies. However, when the asymmetry parameter takes specific multiples of the bosonic mode frequency, level degeneracies reappear-a phenomenon referred to as the hidden symmetry in the asymmetric quantum Rabi model. Identifying the origin of this hidden symmetry and its explicit operator form constitutes two central tasks in studying this system. Here, we investigate the origin of this hidden symmetry using the method of two successive diagonalizations, with a focus on physics in the regime where the ratio between the two-level splitting Δ and the mode frequency ω satisfies Δ/ω ≫ 1. We find that the hidden symmetry stems from energy-level matching within the asymmetric double-well potential, a picture strongly supported by the wavefunctions of both the ground and excited states. Moreover, the emergence of an excited-state quantum phase transition is identified and qualitatively discussed, which arises from the breaking and restoration of this hidden symmetry across different coupling regimes. Our results provide deeper insights into the physics of the asymmetric quantum Rabi model, particularly in the previously less-explored strong-coupling regime, where Δ/ω ≫ 1.
Source: The Journal of Chemical Physics
DOI: 10.1063/5.0299997
Authors: Yun-Tong Yang, Song-Ming Chen, Hong-Gang Luo
Institution: Lanzhou University
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: G7869622521, G8805052026
OpenAlex ID: W4415801876