Dynamic pair-breaking current, critical superfluid velocity, and nonlinear electromagnetic response of nonequilibrium superconductors

Journal Article · Tue Sep 15 00:00:00 EDT 2020 · Physical Review. B

DOI:https://doi.org/10.1103/physrevb.102.104507· OSTI ID:1802034

Sheikhzada, Ahmad  ^[1]; Gurevich, Alex ^[1]

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1. Old Dominion Univ., Norfolk, VA (United States)

Here, we report numerical calculations of a dynamic pair-breaking current density $$J_d$$ and a critical superfluid velocity $$v_d$$ in a nonequilibrium superconductor carrying a uniform, large-amplitude AC current density $$J(t) = J_a$$sinΩ$$\textit{t}$$ with Ω well below the gap frequency Ω $$\ll Δ_0/ℏ$$. The dependencies $$J_d$$(Ω, $$\textit{T}$$) and $$v_d$$(Ω, $$\textit{T}$$) near the critical temperature $$T_c$$ were calculated from either the full time-dependent nonequilibrium equations for a dirty $$\textit{s}$$-wave superconductor or the time-dependent Ginzburg-Landau (TDGL) equations for a gapped superconductor, taking into account the GL relaxation time of the order parameter $$τ_{\text{GL}}$$ and the inelastic electron-phonon relaxation time of quasiparticles $$τ_E$$. We show that both approaches give similar frequency dependencies of $$J_d$$(Ω) and $$v_d$$(Ω) which gradually increase from their static pair-breaking GL values $$J_c$$ and $$v_c$$ at Ω$$τ_E \ll$$1 to $$\sqrt{2}J_c$$ and $$\sqrt{2}v_c$$ at Ω$$τ_E \gg$$ 1. Here $$J_d, v_d$$ and a dynamic superheating field at which the Meissner state becomes unstable were calculated in two different regimes of a fixed AC current and a fixed AC superfluid velocity induced by the applied AC magnetic field $$H = H_a$$ sinΩ$$\textit{t}$$ in a thin superconducting filament or a type-II superconductor with a large GL parameter. We also calculated a nonlinear electromagnetic response of a nonequilibrium superconducting state, particularly a dynamic kinetic inductance and a dissipative quasiparticle conductivity, taking into account the oscillatory dynamics of superconducting condensate and the kinetics of quasiparticles driven by a strong AC current. It is shown that an AC current density produces multiple harmonics of the electric field, the amplitudes of the higher-order harmonics diminishing as $$τ_E$$ increases.

• Research Organization: Old Dominion Univ., Norfolk, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC); National Science Foundation (NSF)
• Grant/Contract Number: SC0010081; PHY 1734075
• OSTI ID: 1802034
• Journal Information: Physical Review. B, Vol. 102, Issue 10; ISSN 2469-9950
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
Materials Science
Physics