Superradiant phase transition in cavity magnonics via Floquet engineering

TL;DR

This paper demonstrates how periodic Floquet modulation can induce and control superradiant phase transitions in cavity magnonics, offering a new method to engineer quantum phase behavior without microwave parametric drives.

Contribution

It introduces a Floquet engineering approach to realize and manipulate superradiant phase transitions in cavity magnonic systems, expanding the toolkit for quantum phase control.

Findings

Discontinuous transition from parity-symmetric to parity-broken phase at a critical Floquet strength.

Continuous recovery of parity symmetry with increasing Floquet field, indicating a second-order transition.

Floquet control enables rich steady-state phases, including bistable and unstable regimes.

Abstract

We propose a scheme to engineer the superradiant phase transition (SPT) in cavity magnonics by periodically modulating the frequency of the magnon mode. The studied system is composed of a yttrium iron garnet (YIG) sphere positioned inside a microwave cavity, where magnons in the YIG sphere are strongly coupled to microwave photons. Under the Floquet drive, the effective frequencies of both the cavity and magnon modes can be readily controlled via the frequency and strength of Floquet field. This tunability allows the cavity magnonic system to support a rich steady-state phase diagram, featuring parity-symmetric, parity-symmetry-broken, bistable, and unstable phases. With the increase of Floquet-field strength, the system exhibit a discontinuous phase transition from the parity-symmetric phase to the parity-symmetry-broken phase at a critical threshold, accompanied by an abrupt jump of the magnon occupation from zero to a finite value. Upon further increase of Floquet-field strength, the magnon occupation declines continuously from a nonzero value back to zero, corresponding to a second-order phase transition that restores the parity-symmetric phase. Additionally, fluctuations in magnon number during the SPT process are examined. Our work establishes an alternative route to engineer the cavity-magnon SPT without relying on microwave parametric drive.