Engineering electron-phonon coupling of quantum defects to a semi-confocal acoustic resonator

• Published in: arXiv.org 2019-06
• Main Authors: Chen, Huiyao, Opondo, Noah F, Jiang, Boyang, MacQuarrie, Evan R, Daveau, Raphaël S, Bhave, Sunil A, Fuchs, Gregory D
• Format: Article
• Language: English
• Subjects: Acoustic coupling; Acoustic resonance; Acoustics; Bulk acoustic wave devices; Coupling; Diamonds; Electron phonon interactions; Electrons; Frequency ranges; Microelectromechanical systems; Microwave antennas; Phonons; Piezoelectricity; Q factors; Rabi frequency; Resonators; Silicon carbide; Strain
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1906.06309

Diamond-based microelectromechanical systems (MEMS) enable direct coupling between the quantum states of nitrogen-vacancy (NV) centers and the phonon modes of a mechanical resonator. One example, diamond high-overtone bulk acoustic resonators (HBARs), feature an integrated piezoelectric transducer and support high-quality factor resonance modes into the GHz frequency range. The acoustic modes allow mechanical manipulation of deeply embedded NV centers with long spin and orbital coherence times. Unfortunately, the spin-phonon coupling rate is limited by the large resonator size, \(>100~\mu\)m, and thus strongly-coupled NV electron-phonon interactions remain out of reach in current diamond BAR devices. Here, we report the design and fabrication of a semi-confocal HBAR (SCHBAR) device on diamond (silicon carbide) with \(f\cdot Q>10^{12}\)(\(>10^{13}\)). The semi-confocal geometry confines the phonon mode laterally below 10~\(\mu\)m. This drastic reduction in modal volume enhances defect center electron-phonon coupling. For the native NV centers inside the diamond device, we demonstrate mechanically driven spin transitions and show a high strain-driving efficiency with a Rabi frequency of \((2\pi)2.19(14)\)~MHz/V\(_{p}\), which is comparable to a typical microwave antenna at the same microwave power.