A material-agnostic platform to probe spin-phonon interactions using high-overtone bulk acoustic wave resonators

TL;DR

This paper presents a material-agnostic method using high-overtone bulk acoustic wave resonators to directly characterize spin-phonon interactions at gigahertz frequencies and millikelvin temperatures, applicable to complex crystalline materials.

Contribution

The authors introduce a novel, versatile technique for probing spin-phonon coupling that overcomes material dependence and fabrication constraints, enabling broader exploration of hybrid quantum systems.

Findings

Achieved spin-phonon coupling measurements in CaWO4 and Y2SiO5.

Demonstrated cooperativity up to 0.5 for erbium dopant ensembles.

Enabled characterization of spin-phonon interactions via acoustic dispersion and dissipation.

Abstract

Spin-phonon interactions have a dual role in emerging spin-based quantum technologies. While they can be a limitation to device performance through decoherence, they also serve as a critical resource for coherent spin control, detection, and the realization of spin-based quantum networks. However, their direct characterization remains a challenge and is usually material-dependent. Here, we introduce a technique to probe spin-phonon coupling at millikelvin temperatures and gigahertz frequencies, using high-overtone bulk acoustic wave resonators (HBARs) integrated with arbitrary crystals via visco-elastic transfer of thin-film lithium niobate transducers. By tuning the Larmor frequency of dilute spin ensembles into resonance with HBAR modes, we extract the anisotropy and strength of spin-phonon interactions from acoustic dispersion and dissipation measurements. We demonstrate this approach in calcium tungstate (CaWO4) and yttrium orthosilicate (Y2SiO5), achieving cooperativities up to 0.5 for erbium dopant ensembles. Our method enables the study of spin-phonon interactions in complex crystalline materials, with minimal fabrication constraints. These results will facilitate the design of hybrid quantum systems and the quest for ion-matrix combination with enhanced spin-phonon coupling.