Abstract
In this research, we tailor the phonon density of states (DOS) in thin superconducting films to suppress quasiparticle losses. We examine a model system of a proximity-enhanced three-layered Al/Nb/Al heterostructure and show that the local quantized phonon spectrum of the ultrathin Al cladding layers in the heterostructure has a pronounced effect on the superconducting resonator’s quality factors. Instead of a monotonic increase of quality factors with decreasing temperatures, we observe the quality factor reaches a maximum at 1.2 K in 5/50/5 nm Al/Nb/Al microstrip resonators, because of a quantized phonon ladder. The phonon DOS may be engineered to enhance the performance of quantum devices.
© Tang, Y.-C., Kwon, S., Mohebbi, H. R., Cory, D. G., & Miao, G.-X. (2017). Phonon engineering in proximity enhanced superconductor heterostructures. Scientific Reports, 7(1). https://doi.org/10.1038/s41598-017-04057-1