Giant Conductance Oscillations in Superconducting Phase Gradiometers

Abstract

A new class of superconductivity-enhanced, quasi-particle interference effects (SEQUINS) is suggested, based on interference from the order parameter phase gradient of a single superconductor (S) in contact with a normal metallic lead (N) of finite width M. By solving the Bogoliubov-de Gennes equation in two dimensions, it is predicted that the electrical conductance will oscillate as the phase gradient w at 90" to the interface is increased, with period V = 2x/M. This effect is enhanced by the presence of a Schottky barrier at the interface and is also present in N-S-N structures. The size of the effect scales with the number of open channels and can be much greater than e 2 / h .

Dissipative electron transport through Andreev interferometers

“…For diffusive structures containing beam splitters a significant increase of the Aharonov-Bohm oscillations of the conductance was shown to exist in Refs. 13,14,[19][20][21][22]24. Beenakker et al 15 showed that the angular distribution of quasi-particles Andreev reflected by a disordered normal-metal -superconductor junction has a narrow peak centerd around the angle of incidence.…”

“…The summation in (19) goes over the N R transverse modes inside the resonant region, which extends over an interval of order ǫ rh v F /L on either side of the Fermi energy; |H 1 is a small addition ∝ ǫ r . The unknown coefficients γ n should be found with the solvability condition of the equation for |H 1 that is readily available from Eq.…”

“…In this way we obtain the main equation which has to be solved in order to get γ n ; these coefficients, according to Eqs. (7) and (19), determine the probability of the resonant transmission of an electron from one reservoir to the other via the sample):…”

“…Knowing γ n we may calculate |H , which contains the coefficients a 3 and b 4 , from Eq. (19). By using Eq.…”

“…The above calculations give a qualitative explanation to analytical and numerical results for the diffusive case presented in Refs. 13,14,[19][20][21][22]24 if the results are obtained for low barrier transparency of the junctions between the sample and the reservoirs.…”