Unconventional magnon excitation by off-resonant microwaves

TL;DR

This paper reveals that magnons can be maximally excited by off-resonant microwaves in a magnetic system using squeezed light, demonstrating a universal quantum effect rooted in quantum fluctuations, with potential applications in quantum information.

Contribution

It introduces a novel off-resonant magnon excitation mechanism using squeezed light, expanding understanding of quantum responses beyond resonance conditions.

Findings

Magnons are maximally excited at frequencies much higher than resonance.

Generated magnons are squeezed, allowing tunable squeezing via magnetic fields.

Off-resonant excitation is universal in hybrid bosonic systems with coherent interactions.

Abstract

It is widely recognized that a physical system can only respond to a periodic driving significantly when the driving frequency matches the normal mode frequency of the system, which leads to resonance. Off-resonant phenomena are rarely considered because of the difficulty to realize strong coupling between physical systems and off-resonant waves. Here we examine the response of a magnetic system to squeezed light and surprisingly find that the magnons are maximally excited when the effective driving frequency is several orders of magnitude larger than the resonant frequency. The generated magnons are squeezed which brings the advantage of tunable squeezing through an external magnetic field. Furthermore, we demonstrate that such off-resonant quasi-particle excitation is universal in all the hybrid systems in which the coherent and parametric interaction of bosons exists and that it is purely a quantum effect, which is rooted in the quantum fluctuations of particles in the squeezed vacuum. Our findings may provide an unconventional route to study off-resonant phenomena and may further benefit the use of hybrid matter-light systems in continuous variable quantum information.