Observation of Double-Dome Superconductivity in Potassium-Doped FeSe Thin Films

Abstract

We report on the emergence of two disconnected superconducting domes in alkali-metal potassium (K)-doped FeSe ultra-thin films grown on graphitized SiC(0001). The superconductivity exhibits hypersensitivity to K dosage in the lower-Tc dome, whereas in the heavily electron-doped higher-Tc dome it becomes spatially homogeneous and robust against disorder, supportive of a conventional Cooper-pairing mechanism. Furthermore, the heavily K-doped multilayer FeSe films all reveal a large superconducting gap of ~ 14 meV, irrespective of film thickness, verifying the higher-Tc superconductivity only in the topmost FeSe layer. The unusual finding of a double-dome superconducting phase has stepped towards the mechanistic understanding of superconductivity in FeSe-derived superconductors.

5 pages, 4 figures

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• Two-dimensional Superconductors with Atomic-scale Thicknesses
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• The Role of SrTiO3 Phonon Penetrating into thin FeSe Films in the Enhancement of Superconductivity
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• High-temperature superconductivity in one-unit-cell FeSe films
• Nanoscale decoupling of electronic nematicity and structural anisotropy in FeSe thin films
• Discrete superconducting phases in FeSe-derived superconductors
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• Interface high-temperature superconductivity
• Spectroscopic Evidence of Superconductivity Pairing at 83 K in Single-Layer FeSe/SrTiO3 Films
• Superconductivity across Lifshitz transition and anomalous insulating state in surface K-dosed (Li0.8Fe0.2OH)FeSe
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• Metamorphoses of electronic structure of FeSe-based superconductors (Review article)
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• Lattice Dynamics of Ultrathin FeSe Films on SrTiO3
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• Absence of superconductivity in ultra-thin layers of FeSe synthesized on a topological insulator
• Pairing Mechanism of the Heavily Electron Doped FeSe Systems: Dynamical Tuning of the Pairing Cutoff Energy
• Electronic structure and nematic phase transition in superconducting multi-layer FeSe films grown by pulsed laser deposition method
• Electronic properties of the FeSe/STO interface from first-principle calculations
• The study of intrinsic defect state of FeSe with scanning tunneling microscopy
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• Electronic Structure of Fe${}_{1.08}$Te bulk crystals and epitaxial FeTe thin films on Bi${}_2$Te${}_3$
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• Insulating Parent Phase and Distinct Doping Evolution to Superconductivity in Single-Layer FeSe/SrTiO3 Films
• Isotropic Cooper Pairs with Emergent Sign Changes in Single-Layer Iron Superconductor
• Interface suppressed nematicity and enhanced superconductivity of FeSe/NdFeO3 in the low doping regime
• Structural Phase Transition, Antiferromagnetism and Two Superconducting Domes in LaFeAsO${}_{1-x}$F${}_x$ (0 $<x\le$ 0.75)
• Importance of Fermi surface and magnetic interactions for the superconducting dome in electron doped FeSe intercalates
• Observation of two distinct superconducting domes under pressure in tetragonal FeS
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• Universal quasi-degenerate orbital origin of two-dome phases in iron pnictide superconductors
• Orbital driven two-dome superconducting phases in multiorbital superconductors
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