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arXiv · 2405.13623

Nonreciprocal Superradiant Phase Transitions and Multicriticality in a Cavity QED System

Gui-Lei Zhu·Chang-Sheng Hu·Hui Wang·Wei Qin·Xin-You Lü·Franco Nori
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Abstract

We demonstrate the emergence of nonreciprocal superradiant phase transitions and novel multicriticality in a cavity quantum electrodynamics (QED) system, where a two-level atom interacts with two counter-propagating modes of a whispering-gallery-mode (WGM) microcavity. The cavity rotates at a certain angular velocity, and is directionally squeezed by a unidirectional parametric pumping $\chi^{(2)}$ nonlinearity. The combination of cavity rotation and directional squeezing leads to nonreciprocal first- and second-order superradiant phase transitions. These transitions do not require ultrastrong atom-field couplings and can be easily controlled by the external pump field. Through a full quantum description of the system Hamiltonian, we identify two types of multicritical points in the phase diagram, both of which exhibit controllable nonreciprocity. These results open a new door for all-optical manipulation of superradiant transitions and multicritical behaviors in light-matter systems, with potential applications in engineering various integrated nonreciprocal quantum devices

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Gui-Lei Zhu, Chang-Sheng Hu, Hui Wang, Wei Qin, Xin-You Lü, Franco Nori. 2024-05-22. Nonreciprocal Superradiant Phase Transitions and Multicriticality in a Cavity QED System. https://doi.org/10.1103/physrevlett.132.193602

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