Titel | Referent | Datum | Ort |
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Gemeinsames TKM-TFP Seminar | Garst, Mirlin, Rockstuhl, Schmalian, Shnirman |
Montag, 14.00-15.30 Uhr |
10-01 |
TFP Institutsseminar | Garst, Rockstuhl |
Di 13.00-14.00 |
10-01 |
IQMT Seminar | Campus Nord, Geb. 425 |
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Physikalisches Kolloquium | Freitag, 15.45-17.15 Uhr |
Lehmann HS |
Seminar über Theoretische Festkörperphysik |
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Speaker: | Christoph Strunk |
Date: | 30/01/2023 14:00 |
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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)