Dresden 2020 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 40: Topological Josephson Junctions

TT 40.2: Talk

Wednesday, March 18, 2020, 15:15–15:30, HSZ 103

Detection of Majorana modes via supercurrents through quantum dots — •Jens Schulenborg and Karsten Flensberg — Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark

Experimental techniques to verify Majorana fermions are of current interest. A prominent test is the effect of Majoranas on the Josephson current between two wires linked via a normal junction.

This talk presents the case of a quantum dot connecting the two superconductors and the sign of the supercurrent in the trivial and topological regimes under grand-canonical equilibrium conditions, explicitly allowing for parity changes due to, e.g., quasi-particle poisoning. We find that the well-known supercurrent reversal for odd quantum dot occupancy (π-junction) in the trivial case[1] does not occur in the presence of Majoranas in the wires. However, we also find this to be a mere consequence of Majoranas being zero energy states, and therefore one cannot conclude that the lack of supercurrent sign reversal is a discriminating signature of Majoranas.

[1] B. I. Spivak et al., Phys. Rev. B 43, 4 (1991)