Quantum tricriticality of chiral-coherent phase in quantum Rabi triangle

TL;DR

This paper investigates the quantum phase transitions in a quantum Rabi triangle system, revealing a chiral-coherent phase with unidirectional photon flow and analyzing its critical behavior within the Dicke universality class.

Contribution

It introduces an analytical framework for the quantum Rabi triangle, uncovering a novel chiral-coherent phase and characterizing its critical properties and symmetry breaking mechanisms.

Findings

Identification of a chiral-coherent phase breaking $ ext{Z}_2$ and chiral symmetry.

Demonstration of unidirectional photon flow tunable by artificial gauge fields.

Confirmation of the phase transition belonging to the Dicke model universality class.

Abstract

The interplay of interactions, symmetries and gauge fields usually leads to intriguing quantum many-body phases. To explore the nature of emerging phases, we study a quantum Rabi triangle system as an elementary building block for synthesizing an artificial magnetic field. We develop an analytical approach to study the rich phase diagram and the associated quantum criticality. Of particular interest is the emergence of a chiral-coherent phase, which breaks both the $\mathbb{Z}_2$ and the chiral symmetry. In this chiral phase, photons flow unidirectionally and the chirality can be tuned by the artificial gauge field, exhibiting a signature of broken time-reversal symmetry. The finite-frequency scaling analysis further confirms the associated phase transition to be in the universality class of the Dicke model. This model can simulate a broad range of physical phenomena of light-matter coupling systems, and may have an application in future developments of various quantum information technologies.