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Dissipation by surface states in superconducting radio-frequency cavities

Author

S. Deyo
M. Kelley
N. Sitaraman
T. Oseroff
D.B. Liarte
Tomas Arias
M. Liepe
J.P. Sethna

Abstract

Recent experiments on superconducting cavities have found that under large rf electromagnetic fields the quality factor can improve with increasing field amplitude, a so-called "anti-Q slope."Linear theories of dissipation break down under these extreme conditions and are unable to explain this behavior. We numerically solve the Bogoliubov-de Gennes equations at the surface of a superconductor in a parallel AC magnetic field, finding that at large fields there are quasiparticle surface states with energies below the bulk value of the superconducting gap. As the field oscillates, such states emerge and disappear with every cycle. We consider the dissipation resulting from inelastic quasiparticle-phonon scattering into these states and investigate the ability of this mechanism to explain features of the experimental observations, including the field dependence of the quality factor. We find that this mechanism is likely not the dominant source of dissipation and does not produce an anti-Q slope by itself; however, we demonstrate in a modified two-fluid model how these bound states can play a role in producing an anti-Q slope. © 2022 American Physical Society.

Date Published

Journal

Physical Review B

Volume

106

Issue

10

URL

https://www.scopus.com/inward/record.uri?eid=2-s2.0-85138178691&doi=10.1103%2fPhysRevB.106.104502&partnerID=40&md5=a5f9c52e999df171e2a9d5af23fe3a58

DOI

10.1103/PhysRevB.106.104502

Group (Lab)

James Sethna Group
Tomas Arias Group

Funding Source

PHY-1549132

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