Dresden 2017 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 33: Transport: Majorana Fermions

TT 33.3: Vortrag

Dienstag, 21. März 2017, 14:30–14:45, HSZ 204

The fermion parity relaxation in the topological Josephson junction — •Oleksiy Kashuba and Björn Trauzettel — Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg

The topological Josephson junction is notable for its Andreev level whose energy is 4π periodic in superconducting phase. Being protected by the fermionic parity conservation, the level is supposed to provide the 4π periodic contribution to the supercurrent in addition to the conventional 2π periodicity caused by other levels. In the static experimental setup, however, even a weakest relaxation of the fermionic parity results in the pure 2π supercurrent periodicity. This problem can be in principle eliminated by the dynamically driven phase on the time scales much smaller than relaxation time. In our work we demonstrate that even in the dynamic experiments, the pseudo-equilibrium occupation of the topological level plays a crucial role, and a number of special requirements has to be met in order to obtain a non-zero 4π periodic behavior. For example: The phase should not be driven uniformly, e.g. in the voltage driven Josephson junction the current contribution from the topological Andreev level is zero; the Josephson junction driven by a constant current, i.e. resistively shunted junction (RSJ) model reveals the 4π periodicity only in the case if both 2π and 4π levels are present.