Suppression of superconductivity and enhanced critical field anisotropy in thin flakes of FeSe

Abstract

FeSe is a unique superconductor that can be manipulated to enhance its superconductivity using different routes while its monolayer form grown on different substrates reaches a record high temperature for a two-dimensional system. In order to understand the role played by the substrate and the reduced dimensionality on superconductivity, we examine the superconducting properties of exfoliated FeSe thin flakes by reducing the thickness from bulk down towards 9 nm. Magnetotransport measurements performed in magnetic fields up to 16T and temperatures down to 2K help to build up complete superconducting phase diagrams of different thickness flakes. While the thick flakes resemble the bulk behaviour, by reducing the thickness the superconductivity of FeSe flakes is suppressed. In the thin limit we detect signatures of a crossover towards two-dimensional behaviour from the observation of the vortex-antivortex unbinding transition and strongly enhanced anisotropy. Our study provides detailed insights into the evolution of the superconducting properties from three-dimensional bulk behaviour towards the two-dimensional limit of FeSe in the absence of a dopant substrate.

arXiv comment18 pages, 13 figures

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• Superconducting Quantum Interference in Twisted van der Waals Heterostructures
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• The drastic effect of the impurity scattering on the electronic and superconducting properties of Cu-doped FeSe
• Signatures of a Quantum Griffiths Phase close to an Electronic Nematic Quantum Phase Transition
• Twisted-bilayer FeSe and the Fe-based superlattices
• Interface superconductivity in FeSe thin films on SrTiO${}_3$grown by the PLD technique
• Multi-band description of the upper critical field of bulk FeSe
• Unconventional localization of electrons inside of a nematic electronic phase
• High-$T_c$ Berezinskii-Kosterlitz-Thouless transition in 2D superconducting systems with coupled deep and quasi-flat electronic bands with van Hove singularities
• Anisotropy of upper critical fields and interface superconductivity in FeSe/SrTiO3 grown by PLD
• High quality Fe1+yTe synthesized by chemical vapor deposition with conspicuous vortex flow
• From orbital to paramagnetic pair breaking in layered superconductor 2H-NbS${}_2$
• Freestanding Thin-Film Materials
• Unusual normal and superconducting state properties observed in hydrothermal Fe1-xSe flakes
• Temperature dependence and limiting mechanisms of the upper critical field of FeSe thin films
• Fluctuating Cooper pairs in FeSe at temperatures exceeding double Tc
• Studies of superconductivity of Fe chalcogenides in films grown by PLD technique
• Thermodynamic parameters of atomically thin superconductors derived from the upper critical field
• Predictive power of the Berezinskii-Kosterlitz-Thouless theory based on Renormalization Group throughout the BCS-BEC crossover in 2D superconductors
• Growth Optimization of MoSi Thin Film and Measurement of Transport Critical Current Density of its Meander Structure
• Fragile pressure-induced magnetism in FeSe superconductors with a thickness reduction