Weak-field dissipative conductivity of a dirty superconductor with Dynes subgap states under a dc bias current up to the depairing current density
Abstract
We study the dissipative conductivity σ1 of a dirty superconductor with a finite Dynes parameter Γ under a dc-biased weak time-dependent field. The Usadel equation for the current-carrying state is solved to calculate the pair potential, penetration depth, supercurrent density, and quasiparticle spectrum. It is shown that, while the depairing current density jd for Γ =0 is coincident with the Kupriyanov-Lukichev theory, a finite Γ decreases the superfluid density, resulting in a reduction of jd. The broadening of the peaks of the quasiparticle density of states induced by a combination of a finite Γ and a dc bias can reduce σ1 below that for the ideal dirty BCS superconductor with Γ =0 , while subgap states at Fermi level proportional to Γ results in a residual conductivity at T →0 . We find the optimum combination of Γ and the dc bias to minimize σ1 by scanning all Γ and all currents up to jd. By using the results, it is possible to improve jd and reduce electromagnetic dissipation in various superconducting quantum devices.
- Publication:
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Physical Review Research
- Pub Date:
- March 2020
- DOI:
- 10.1103/PhysRevResearch.2.013302
- arXiv:
- arXiv:1912.01822
- Bibcode:
- 2020PhRvR...2a3302K
- Keywords:
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- Condensed Matter - Superconductivity;
- Physics - Accelerator Physics
- E-Print:
- 9 pages, 8 figures