Thema der Dissertation:
Yu-Shiba-Rusinov states in atomic-scale Josephson junctions
Yu-Shiba-Rusinov states in atomic-scale Josephson junctions
Abstract: Josephson junctions feature highly nonlinear electronic characteristics whose properties become especially relevant at the atomic scale, where quantum effects dominate. Recent studies have explored junctions with broken symmetries, leading to the Josephson diode effect: non-reciprocal current flow depending on bias direction, analogous to conventional diodes.
We present a microscopic analysis of this effect in weakly-damped, current-driven junctions using a generalized resistively and capacitively shunted junction model with stochastic dynamics. We show that non-reciprocity in switching and retrapping currents arises from distinct mechanisms, each requiring different symmetry-breaking conditions. This distinction helps identify the microscopic origins of diode-like behavior.
In particular, we focus on atomic-scale junctions hosting Yu-Shiba-Rusinov (YSR) states, which emerge from magnetic impurities on superconductors and can break particle-hole symmetry. This asymmetry affects quasiparticle transport and explains experimentally observed diode behavior. Using a non-equilibrium Green’s function approach, we calculate the quasiparticle current, including its higher harmonics as well as shot noise.
Under voltage bias and high-frequency irradiation, junctions can be engineered such that transport is dominated by photon-assisted Andreev reflections mediated by the YSR state. The resulting conductance features deviate from standard theory but match experiments. These effects enable precise measurement of small subgap energies, helping distinguish them from zero-energy states such as Majorana states.
We present a microscopic analysis of this effect in weakly-damped, current-driven junctions using a generalized resistively and capacitively shunted junction model with stochastic dynamics. We show that non-reciprocity in switching and retrapping currents arises from distinct mechanisms, each requiring different symmetry-breaking conditions. This distinction helps identify the microscopic origins of diode-like behavior.
In particular, we focus on atomic-scale junctions hosting Yu-Shiba-Rusinov (YSR) states, which emerge from magnetic impurities on superconductors and can break particle-hole symmetry. This asymmetry affects quasiparticle transport and explains experimentally observed diode behavior. Using a non-equilibrium Green’s function approach, we calculate the quasiparticle current, including its higher harmonics as well as shot noise.
Under voltage bias and high-frequency irradiation, junctions can be engineered such that transport is dominated by photon-assisted Andreev reflections mediated by the YSR state. The resulting conductance features deviate from standard theory but match experiments. These effects enable precise measurement of small subgap energies, helping distinguish them from zero-energy states such as Majorana states.
Zeit & Ort
04.05.2026 | 16:00
* Bitte beachten: Die Disputation ist nicht öffentlich! *
FB-Raum (1.1.16)
(Fachbereich Physik, Arnimallee 14, 14195 Berlin)