Abstract
We investigate the effects of Dynes pair-breaking scattering rate $\Gamma$ on the superfluid flow in a narrow thin-film superconductor and a semi-infinite superconductor by self-consistently solving the coupled Maxwell and Usadel equations for the BCS theory in the diffusive limit for all temperature $T$, all $\Gamma$, and all superfluid momentum. We obtain the depairing current density $j_d(\Gamma, T)$ and the current-dependent nonlinear kinetic inductance $L_k(j_s, \Gamma, T)$ in a narrow thin-film and the superheating field $H_{sh}(\Gamma, T)$ and the current distribution in a semi-infinite superconductor, taking the nonlinear Meissner effect into account. The analytical expressions for $j_d(\Gamma,T)|_{T=0}$, $L_k(j_s, \Gamma, T)|_{T=0}$, and $H_{sh}(\Gamma, T)|_{T=0}$ are also derived. The theory suggests $j_d$ and $H_{sh}$ can be ameliorated by reducing $\Gamma$, and $L_k$ can be tuned by a combination of the bias current and $\Gamma$. Tunneling spectroscopy can test the theory and also give insight into how to engineer $\Gamma$ via materials processing. Implications of the theory would be useful to improve performances of various superconducting quantum devices.
Highlights
The physics of the superfluid flow in s-wave superconductors is closely tied with the operating principles and performances of various superconducting quantum devices such as superconducting nanowire single-photon detectors (SNSPDs) [1,2], resonators for microwave kinetic inductance detectors (MKIDs) [3,4] and quantum computers [5,6,7], and superconducting radio-frequency (SRF) resonant cavities for particle accelerators [8,9,10,11]
We focus on effects of on the superfluid flow in disordered superconductors
We consider the geometries shown in Fig. 2: a thin and narrow superconducting film and a semi-infinite superconductor
Summary
The physics of the superfluid flow in s-wave superconductors is closely tied with the operating principles and performances of various superconducting quantum devices such as superconducting nanowire single-photon detectors (SNSPDs) [1,2], resonators for microwave kinetic inductance detectors (MKIDs) [3,4] and quantum computers [5,6,7], and superconducting radio-frequency (SRF) resonant cavities for particle accelerators [8,9,10,11]. Theories including realistic materials features which can limit device performances have been studied to a lesser extent Such theories would be useful to pin down causes of performance limitations, e.g., critical current below the ideal jd in nanowires and quenches below the ideal Hsh in SRF cavities, etc. We consider the geometries shown in Fig. 2: a thin and narrow superconducting film (relevant to, e.g., SNSPD, MKID) and a semi-infinite superconductor (relevant to, e.g., SRF cavities made from bulk materials or thick film). We evaluate the depairing current density jd ( , T ), the current-dependent nonlinear kinetic inductance Lk ( js, , T ), and the superheating field Hsh( , T ) for all T , all. We calculate the current distribution taking the nonlinear Meissner effect into account and evaluate the superheating field Hsh( , T ).
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