Electron-phonon interaction in superconducting point contacts
Abstract
The current-voltage characteristic of a superconducting point contact, whose size a is much smaller than all characteristic lengths, is found: a ⪡ξ(0), l, ʋF/ωD (l is the impurity scattering length, and ξ(0) is the superconducting coherence length). In a region of dimension a near the contact, where there is a strong electric field, nonequilibrium phonons are emitted by quasiparticles, as a result of which the current-voltage characteristic has singularities related to the position of the peaks in the electron-phonon interaction function G(ω) (the analog of the Éliashberg function including the geometry of the contact). The excess current, existing at high voltages eV⪢Δ, decreases with increasing V, and the derivative dIexc/dV is proportional to the function G(ω), differing somewhat from the point contact electron-phonon interaction function in the case of a normal contact.