Multi-band description of the upper critical field of bulk FeSe

Abstract

The upper critical field of multi-band superconductors can be an essential quantity to unravel the nature of superconducting pairing and its interplay with the electronic structure. Here we experimentally map out the complete upper critical field phase diagram of FeSe for different magnetic field orientations at temperatures down to 0.3 K using both resistivity and torque measurements. The temperature dependence of the upper critical field reflects that of a multi-band superconductor and requires a two-band description in the clean limit with band coupling parameters favouring interband over intraband interactions. Despite the relatively small Maki parameter in FeSe of $\alpha \sim 1.6$, the multi-band description of the upper critical field is consistent with the stabilization of a FFLO state below $T/T_{\mathrm{c}}\sim 0.3$. We find that the anomalous behaviour of the upper critical field is linked to a departure from the single-band picture, and FeSe provides a clear example where multi-band effects and the strong anisotropy of the superconducting gap need to be taken into account.

arXiv comment15 pages, 10 figures (manuscript and the supplemental materials

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Cited by in corpus (5)

• Reducing the strain required for ambient-pressure superconductivity in bilayer nickelates
• Upper critical magnetic field and multiband superconductivity in artificial high-Tc superlattices of nano quantum wells
• Temperature dependence and limiting mechanisms of the upper critical field of FeSe thin films
• Impact of Disorder on the Superconducting Properties and BCS-BEC Crossover in FeSe Single Crystals
• High magnetic field response of superconductivity dome in quantum artificial High Tc superlattices with variable geometry