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.

33 pages, 32 figures, invited review article

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Cited by in corpus (21)

• Ironing out the details of unconventional superconductivity
• On the Remarkable Superconductivity of FeSe and its Close Cousins
• Pure nematic quantum critical point accompanied by a superconducting dome
• Two superconducting states with broken time-reversal symmetry in FeSe1-xSx
• Protonation-induced discrete superconducting phases in bulk FeSe single crystals
• Superconductivity-induced spectral weight transfer due to quantum geometry
• Electronic transport properties and hydrostatic pressure effect of FeSe${}_{0.67}$Te${}_{0.33}$ single crystals free of phase separation
• All-optical generation of Abrikosov vortices by the Inverse Faraday Effect
• Control of band structure of FeSe single crystals via biaxial strain
• Pressure-induced reconstitution of Fermi surfaces and spin fluctuations in S-substituted FeSe
• Spin fluctuations from Bogoliubov Fermi surfaces in the superconducting state of S-substituted FeSe
• Nematic state of the FeSe superconductor
• Cometal addition effect on superconducting properties and granular behaviours of polycrystalline FeSe0.5Te0.5
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