Thermodynamics of Non-Hermitian Josephson junctions with exceptional points
ORAL
Abstract
We present an analytical formulation of the thermodynamics, free energy and entropy, of any generic Bogoliubov de Genes model which develops exceptional point (EP) bifurcations in its complex spectrum when coupled to reservoirs. We apply our formalism to a non-Hermitian Josephson junction where, despite recent claims, the supercurrent does not exhibit any divergences at EPs. The entropy, on the contrary, shows a universal jump of 1/2 log(2) which can be linked to the emergence of Majorana zero modes (MZMs) at EPs. Our method allows us to obtain precise analytical boundaries for the temperatures at which such Majorana entropy steps appear. We propose a generalized Maxwell relation linking supercurrents and entropy which could pave the way towards the direct experimental observation of such steps in e.g. quantum-dot-based minimal Kitaev chains.
*DMP and RA acknowledge financial support from the Horizon Europe Framework Program of the European Commission through the European Innovation Council Pathfinder Grant No. 101115315 (QuKiT); the Spanish Ministry of Science through Grants No. PID2021-125343NB-I00 and No. TED2021-130292B-C43 funded by MCIN/AEI/10.13039/501100011033, "ERDF A way of making Europe" and European Union Next Generation EU/PRTR, as well as the CSIC Interdisciplinary Thematic Platform (PTI+) on Quantum Technologies (PTI-QTEP+). YM acknowledges support from the European Research Council (ERC) under the European Unions Horizon 2020 research and innovation program under Grant Agreement No. 951541 and the Israel Science Foundation Grant No. 154/19.
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Publication:Thermodynamics of Non-Hermitian Josephson junctions with exceptional points (https://doi.org/10.48550/arXiv.2405.02387)
