Regular events
Titel Referent Datum Ort

Garst, Mirlin, Rockstuhl, Schmalian, Shnirman

Montag, 14.00-15.30 Uhr

10-01

Garst, Rockstuhl

Di 13.00-14.00

10-01

Campus Nord, Geb. 425

Freitag, 15.45-17.15 Uhr

Lehmann HS

Supercurrent diodes, squeezed vortices and other insights from inductance measurements

Seminar über Theoretische Festkörperphysik

Speaker:

Christoph Strunk

Date:

30/01/2023 14:00

Where:

10.01

Affiliation:

University of Regensburg

Host:

Igor Gornyi

Abstract

The recent discovery of intrinsic supercurrent diode effect [1], and its prompt observation in a rich variety of systems, has shown that nonreciprocal supercurrents naturally emerge when both space- and time-inversion symmetries are broken. I will report on ac-manifestations of the diode effect in the non-linear inductance in planar Josephson junctions, based on a ballistic Al/InAs-heterostructure, that is exposed to an in-plane magnetic field Bip [2]. At low Bip a non-reciprocal term is found in the induc­tance that is linear in Bip. At higher Bip a sign reversal of the super­current diode effect is observed that can be traced back to a zero-pi-like transition in the current-phase relation.
In a small perpendicular magnetic field, also the unpatterned heterostructure features a large inductance which results from the oscillations of vortices around pinning centers. The vortex inductance is inversely proportional to the pinning potential. If a parallel field is applied in addition, the pinning potential strongly increases in an anisotropic fashion. This result can be under­stood as a manifestation of Lifschitz invariants in our non-centro­sym­metric hetero­structure [3].
Finally, we investigate ultra-thin disordered NbN-films. We observe a sharp Berezinskii-Kosterlitz-Thouless (BKT) transition in both DC- and AC transport properties. Four independent observables allow for a consistent determination of the mean-field and BKT transition temperatures, as well as the superfluid stiffness. Our results demonstrate the absence of an intrinsic broadening of the BKT-transition in the presence of strong disorder and provide a reliable basis for the study of more complex non-equilibrium phenomena near the BKT-transition.

[1] F. Ando et al., Nature 584, 373 (2020)
[2] C. Baumgartner, et al., Nature Nanotech. 17, 39 (2022).
[3] L. Fuchs, et al., Phys. Rev. X 12, 041020 (2022)