Superconducting Stiffness and Coherence Length of FeSe$_{0.5}$Te$_{0.5}$ Measured in Zero-Applied Field

Amotz Peri; Itay Mangel; Amit Keren

doi:10.3390/condmat8020039

paper

Superconducting Stiffness and Coherence Length of FeSe $_{0.5}$ Te $_{0.5}$ Measured in Zero-Applied Field

arXiv:2305.01926 · doi:10.3390/condmat8020039

Abstract

Superconducting stiffness $ρ_{s}$ and coherence length $ξ$ are usually determined by measuring the penetration depth $λ$ of a magnetic field and the upper critical field $H_{c 2}$ of a superconductor (SC), respectively. However, in magnetic SC, e.g. some of the iron-based, this could lead to erroneous results since the internal field could be very different from the applied one. To overcome this problem in Fe $_{1 + y}$ Se $_{x}$ Te $_{1 - x}$ with $x \sim 0.5$ and $y \sim 0$ (FST), we measure both quantities with the Stiffnessometer technique. In this technique, one applies a rotor-free vector potential $A$ to a superconducting ring and measures the current density $j$ via the ring's magnetic moment $m$ . $ρ_{s}$ and $ξ$ are determined from London's equation $j = - ρ_{s} A$ and its range of validity. This method is particularly accurate at temperatures close to the critical temperature $T_{c}$ . We find weaker $ρ_{s}$ and longer $ξ$ than existing literature reports, and critical exponents which agree better with expectations based on the Ginzburg-Landau theory.

10 pages, 10 figures

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Superconducting Stiffness and Coherence Length of FeSe0.5​Te0.5​ Measured in Zero-Applied Field

Abstract

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Superconducting Stiffness and Coherence Length of FeSe $_{0.5}$ Te $_{0.5}$ Measured in Zero-Applied Field