Engineering nonequilibrium superconducting phases in a voltage-driven superconductor under an external magnetic field

Fuente: arXiv
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Main Authors: Kawamura, Taira, Ohashi, Yoji
Format: Preprint
Published: 2025
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author Kawamura, Taira
Ohashi, Yoji
author_facet Kawamura, Taira
Ohashi, Yoji
contents We theoretically investigate nonequilibrium properties of a normal metal-superconductor-normal metal (NSN) junction under an external magnetic field. When a bias voltage is applied between the normal-metal leads, the confined superconductor is driven out of equilibrium, resulting in a nonequilibrium quasiparticle distribution function having a two-step structure. Using the nonequilibrium Green's function technique, we determine a comprehensive phase diagram of the nonequilibrium superconductor. Our analysis reveals that the interplay between Zeeman-split energy bands and the nonequilibrium distribution function gives rise to a rich phase structure. Notably, we find that superconductivity destroyed by a strong external magnetic field revives by applying the bias voltage. This reentrant phenomenon is shown to originate from four effective "Fermi surfaces" that result from the combination of Zeeman-split energy bands and the two-step structure in the nonequilibrium distribution function. Our results demonstrate the possibility of controlling quantum states of matter through the combined engineering of energy band structures and distribution functions.
format Preprint
id arxiv_https___arxiv_org_abs_2503_04179
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Engineering nonequilibrium superconducting phases in a voltage-driven superconductor under an external magnetic field
Kawamura, Taira
Ohashi, Yoji
Superconductivity
We theoretically investigate nonequilibrium properties of a normal metal-superconductor-normal metal (NSN) junction under an external magnetic field. When a bias voltage is applied between the normal-metal leads, the confined superconductor is driven out of equilibrium, resulting in a nonequilibrium quasiparticle distribution function having a two-step structure. Using the nonequilibrium Green's function technique, we determine a comprehensive phase diagram of the nonequilibrium superconductor. Our analysis reveals that the interplay between Zeeman-split energy bands and the nonequilibrium distribution function gives rise to a rich phase structure. Notably, we find that superconductivity destroyed by a strong external magnetic field revives by applying the bias voltage. This reentrant phenomenon is shown to originate from four effective "Fermi surfaces" that result from the combination of Zeeman-split energy bands and the two-step structure in the nonequilibrium distribution function. Our results demonstrate the possibility of controlling quantum states of matter through the combined engineering of energy band structures and distribution functions.
title Engineering nonequilibrium superconducting phases in a voltage-driven superconductor under an external magnetic field
topic Superconductivity
url https://arxiv.org/abs/2503.04179