Failure of the mean-field description of magnetic fluctuations in the superconducting quantum dot

0559628 - FZÚ 2023 RIV US eng J - Journal Article
Janiš, Václav - Yan, Jiawei
Failure of the mean-field description of magnetic fluctuations in the superconducting quantum dot.
AIP Advances. Roč. 12, č. 3 (2022), č. článku 035139. E-ISSN 2158-3226
R&D Projects: GA MŠMT LTC19045; GA ČR GA19-13525S
Institutional support: RVO:68378271
Keywords : mean-field * magnetic fluctuations * thermal fluctuations * dynamical renormalization
OECD category: Condensed matter physics (including formerly solid state physics, supercond.)
Impact factor: 1.6, year: 2022
Method of publishing: Open access

The zero-temperature physics of interacting quantum dots attached to superconducting leads is now well understood. The overall qualitative picture is obtained from the static mean-field approximation. The situation drastically changes at non-zero temperatures. No reliable solutions apart from numerical simulations exist there. We show that any static mean-field approximation fails at non-zero temperatures since magnetic fluctuations induce dynamical corrections that lead to broadening of the in-gap state energies to energy bands. Spin-symmetric equilibrium state at non-zero temperatures is unstable with respect to magnetic fluctuations and the zero magnetic field can be reached only as a weak limit of the spin-polarized solution like in a magnetically ordered phase.
Permanent Link: https://hdl.handle.net/11104/0333617