K. Kopnin
Collaborator: V.M. Vinokur
Phenomena under consideration include vortex structure and dynamics, transport in point contacts, tunnel junctions, and nanowires. The Andreev bound states in vortex cores, point contacts and other heterostructures are being studied; the crucial effects of these states in the transport phenomena are being clarified.
A new class of superfluid turbulence is discovered experimentally under conditions that the normal component is clamped in the container frame due to high viscosity. The transition to superfluid turbulence is found to be velocity independent; it is determined by the ratio of the mutual friction parameter that depends on temperature. A theoretical model is proposed that describes the onset of turbulence.
The electronic transport in clean multichannel superconducting point contacts is studied. A scattering by small amount of impurities is shown to lead to an effective momentum relaxation at low voltages that results in a linear voltage dependence of the current through the contact. For high voltages, electrons do not have time to relax, and the transport is ballistic. The theory of single-electron transport is developed in clean and disordered Andreev wires, i.e., normal conductors surrounded by a superconductor. Vortices in type II superconductors are examples of such Andreev wires. Clean Andreev wires are shown to be similar to usual normal wires: the transport is associated with the transverse Andreev modes.