INFLUENCE OF MAGNETIC FIELD ON CONDUCTIVITY OF SUPERCONDUCTOR—INSULATOR — NORMAL METAL TUNNEL STRUCTURE

The results of experiments on the effect of a magnetic field on the conductivity of superconductor — insulator — normal metal tunnel structures are analyzed at temperatures much lower than the critical temperature of the superconductor Tc and at low voltages at which the single-electron current Isingle is comparable to or less than the sub-gap Andreev current IA= In+Is. These two components of the Andreev current are associated with the diffusive motion of correlated pairs of electronic excitations in the normal and, accordingly, superconducting layers of the structure. With the orientation of the field perpendicular to the structure with lateral dimensions greater than the penetration depth, the transition from an inhomogeneous field distribution to a vortex structure is traced. At field orientations both in the plane of the structure and perpendicular to it, the single-electron current increases due to the influence of the field on the superconducting gap Δc. The conductivity due to the Andreev current In =kntanh(eV/2kTeff) decreases due to an increase in the effective temperature Teff. The decrease in the Is contribution is associated with a decrease of the gap. We do not know of any works that consider the influence of the magnetic field on this component of the tunneling current. It is shown that at low voltages, the so-called Dynes current, due to an imaginary addition to the gap energy due to the influence of defects in the superconductor, does not contribute to the conductivity of the tunnel structure.