Nonequilibrium transport via spin-induced sub-gap states in superconductor/quantum dot/normal metal cotunnel junctions

TY - JOUR

T1 - Nonequilibrium transport via spin-induced sub-gap states in superconductor/quantum dot/normal metal cotunnel junctions

AU - Koerting, Verena

AU - Andersen, Brian Møller

AU - Flensberg, Karsten

AU - Paaske, Jens

PY - 2010/12/8

Y1 - 2010/12/8

N2 - We study low-temperature transport through a Coulomb blockaded quantum dot (QD) contacted by a normal (N) and a superconducting (S) electrode. Within an effective cotunneling model the conduction electron self-energy is calculated to leading order in the cotunneling amplitudes and subsequently resummed to obtain the nonequilibrium T matrix, from which we obtain the nonlinear cotunneling conductance. For even-occupied dots the system can be conceived as an effective S/N-cotunnel junction with subgap transport mediated by Andreev reflections. The net spin of an odd-occupied dot, however, leads to the formation of subgap resonances inside the superconducting gap which give rise to a characteristic peak-dip structure in the differential conductance, as observed in recent experiments.

AB - We study low-temperature transport through a Coulomb blockaded quantum dot (QD) contacted by a normal (N) and a superconducting (S) electrode. Within an effective cotunneling model the conduction electron self-energy is calculated to leading order in the cotunneling amplitudes and subsequently resummed to obtain the nonequilibrium T matrix, from which we obtain the nonlinear cotunneling conductance. For even-occupied dots the system can be conceived as an effective S/N-cotunnel junction with subgap transport mediated by Andreev reflections. The net spin of an odd-occupied dot, however, leads to the formation of subgap resonances inside the superconducting gap which give rise to a characteristic peak-dip structure in the differential conductance, as observed in recent experiments.

U2 - 10.1103/PhysRevB.82.245108

DO - 10.1103/PhysRevB.82.245108

M3 - Journal article

SN - 0163-1829

VL - 82

SP - 245108

JO - Physical Review B Condensed Matter

JF - Physical Review B Condensed Matter

IS - 24

ER -