First-Order Transitions in Weak Ising Spin-Orbit-Coupled Superconductors

Fuente: arXiv
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Main Authors: Wang, Xusheng, Tang, Gaomin, Ji, Shuai-hua
Format: Preprint
Published: 2026
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author Wang, Xusheng
Tang, Gaomin
Ji, Shuai-hua
author_facet Wang, Xusheng
Tang, Gaomin
Ji, Shuai-hua
contents Ising spin-orbit coupling (ISOC) can strongly protect superconductivity against exchange-field-induced depairing, typically leading to critical fields far exceeding the Pauli limit and continuous (second-order) phase transitions. Here, using a free-energy approach, we demonstrate that first-order transitions can emerge in superconductors with weak ISOC under large exchange fields. In this regime, conventional theoretical approaches based on the gap equation fail to determine the thermodynamic critical field and instead yield only the supercooling field. Moreover, we identify two pronounced in-gap coherence peaks in the quasiparticle spectra, which represent the weak-ISOC manifestation of the previously reported mirage-gap states. Our results establish the importance of free-energy analysis in describing the first-order phase transitions in Ising superconductors and reveal distinct spectroscopic signatures of the weak-ISOC regime.
format Preprint
id arxiv_https___arxiv_org_abs_2605_03774
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle First-Order Transitions in Weak Ising Spin-Orbit-Coupled Superconductors
Wang, Xusheng
Tang, Gaomin
Ji, Shuai-hua
Superconductivity
Ising spin-orbit coupling (ISOC) can strongly protect superconductivity against exchange-field-induced depairing, typically leading to critical fields far exceeding the Pauli limit and continuous (second-order) phase transitions. Here, using a free-energy approach, we demonstrate that first-order transitions can emerge in superconductors with weak ISOC under large exchange fields. In this regime, conventional theoretical approaches based on the gap equation fail to determine the thermodynamic critical field and instead yield only the supercooling field. Moreover, we identify two pronounced in-gap coherence peaks in the quasiparticle spectra, which represent the weak-ISOC manifestation of the previously reported mirage-gap states. Our results establish the importance of free-energy analysis in describing the first-order phase transitions in Ising superconductors and reveal distinct spectroscopic signatures of the weak-ISOC regime.
title First-Order Transitions in Weak Ising Spin-Orbit-Coupled Superconductors
topic Superconductivity
url https://arxiv.org/abs/2605.03774