Physics Dept Seminar

June 17th, Wednesday (*SPECIAL DAY*)

Multimode magnon-phonon cavity driven by symmetry-locked strain fields

Prof. Wencan Jin

Dept. of Physics, Auburn Univ.

(Condensed Matter Physics, Host: Junjie Yang)

Room: ECE 202

Time: 11:45 am - 12:45 pm with 11:30 am teatime

Strong coupling between two quantized excitations in a cavity can give rise to hybridized states that bestow novel quantum phenomena and device applications. In particular, hybrid magnon-phonon cavities with precise control knobs are highly sought after for coherent energy and signal transduction in solid-state platforms. However, engineering strain at the meso- or nanoscale to control magnon-phonon hybridization remains a major challenge, as spatially inhomogeneous strain typically introduces additional damping and reduced coherence, thereby hindering device integration and scalability.

In this talk, I will present an epitaxial La0.7Sr0.3MnO3/SrTiO3 (LSMO/STO) heterostructure, in which anisotropic local strain fields are naturally generated at the interface through the formation of structural domains during the cubic-to-tetragonal phase transition in STO. Remarkably, a small anisotropic local strain of less than 0.1% is sufficient to drive pronounced splitting of the magnon into three branches. Each branch independently hybridizes with acoustic phonons, forming a matrix of magnon-phonon avoided crossings. This platform enables multimode transduction and programmable networks in frequency and magnetic field space.

These results suggest that local strain fields, traditionally regarded as disorders, can instead serve as a sensitive mechanism for generating multistate magnon-phonon hybridization – a new route for designing tunable hybrid magnonic and phononic devices. Finally, I will highlight our recent advances in optical second harmonic generation techniques in detecting disordered phases in a quantum ferroelectric metal.