Admittance of a long diffusive SNS junction

The dynamical properties of hybrid normal metal/superconductor structures have recently come into research focus both experimentally and theoretically. Recent experimental studies of the coherent admittance Y (ω ) of SNS rings as a function of the phase difference ϕ₀ are still not fully understood. Here we concentrate on the linear response regime, calculating Y (ω ) by solving the Usadel equations, linearized in an electric field. Partially reproducing previously known results, we find qualitatively different behavior in the collisionless regime of τ_in^-1≪ω ≲E_Th and high temperature T ≫E_Th and low temperature T ≲E_Th near the minigap closing ϕ₀∼π . We find that the dissipative part ReY (ω ) peaks when the minigap closes (at a phase difference of π ) even at high temperatures, when the equilibrium supercurrent is fully suppressed.