Exotic Superconducting States in FeSe-based Materials

Abstract

High-temperature superconductivity and a wide variety of exotic superconducting states discovered in FeSe-based materials have been at the frontier of research on condensed matter physics over the past decade. Unique properties originating from the multiband electronic structure, strongly orbital-dependent phenomena, extremely small Fermi energy, electronic nematicity, and topological aspects give rise to many distinct and fascinating superconducting states. Here, we provide an overview of our current understanding of the superconductivity of {\it bulk} FeSe-based materials, focusing on FeSe and the isovalent substituted FeSe${}_{1-x}$S${}_x$ and FeSe${}_{1-x}$Te${}_x$. We discuss the highly nontrivial superconducting properties in FeSe, including extremely anisotropic pairing states, crossover phenomena from Bardeen--Cooper--Schrieffer (BCS) to Bose--Einstein condensation (BEC) states, a novel field-induced superconducting phase, and broken time-reversal symmetry. We also discuss the evolution of the superconducting gap function with sulfur and tellurium doping, paying particular attention to the impact of quantum critical nematic fluctuations and the topological superconductivity. FeSe-based materials provide an excellent playground to study various exotic superconducting states.

arXiv comment33 pages, 32 figures, invited review article

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Cited by in corpus (75)

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• On the Remarkable Superconductivity of FeSe and its Close Cousins
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• When Superconductivity Crosses Over: From BCS to BEC
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• Protonation-induced discrete superconducting phases in bulk FeSe single crystals
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• Non-local $d_{xy}$ nematicity and the missing electron pocket in FeSe
• Superconductivity-induced spectral weight transfer due to quantum geometry
• Bond Directional Anapole Order in a Spin-Orbit Coupled Mott Insulator Sr${}_2$(Ir${}_{1-x}$Rh${}_x$)O${}_4$
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• All-optical generation of Abrikosov vortices by the Inverse Faraday Effect
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• Pure nematic state in iron-based superconductor
• Positive and negative chemical pressure effects investigated in electron-doped FeSe films with an electric-double-layer structure
• Using Disorder to Identify Bogoliubov Fermi-Surface States
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• Cometal addition effect on superconducting properties and granular behaviours of polycrystalline FeSe0.5Te0.5
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