20 K superconductivity in heavily electron doped surface layer of FeSe bulk crystal

Abstract

A superconducting transition temperature Tc as high as 100 K was recently discovered in 1 monolayer (1ML) FeSe grown on SrTiO3 (STO). The discovery immediately ignited efforts to identify the mechanism for the dramatically enhanced Tc from its bulk value of 7 K. Currently, there are two main views on the origin of the enhanced Tc; in the first view, the enhancement comes from an interfacial effect while in the other it is from excess electrons with strong correlation strength. The issue is controversial and there are evidences that support each view. Finding the origin of the Tc enhancement could be the key to achieving even higher Tc and to identifying the microscopic mechanism for the superconductivity in iron-based materials. Here, we report the observation of 20 K superconductivity in the electron doped surface layer of FeSe. The electronic state of the surface layer possesses all the key spectroscopic aspects of the 1ML FeSe on STO. Without any interface effect, the surface layer state is found to have a moderate Tc of 20 K with a smaller gap opening of 4 meV. Our results clearly show that excess electrons with strong correlation strength alone cannot induce the maximum Tc, which in turn strongly suggests need for an interfacial effect to reach the enhanced Tc found in 1ML FeSe/STO.

5 pages, 4 figures

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Cited by in corpus (20)

• The Role of SrTiO3 Phonon Penetrating into thin FeSe Films in the Enhancement of Superconductivity
• Ubiquitous strong electron phonon coupling at the interface of FeSe/SrTiO3
• Dynamic interfacial polaron enhanced superconductivity of FeSe/SrTiO3
• The Nematic Energy Scale and the Missing Electron Pocket in FeSe
• High-temperature superconductivity in one-unit-cell FeSe films
• How correlated is the FeSe/SrTiO${}_3$ system ?
• Spectroscopic Evidence of Superconductivity Pairing at 83 K in Single-Layer FeSe/SrTiO3 Films
• Lattice Dynamics of Ultrathin FeSe Films on SrTiO3
• Superconductivity without hole-pocket in electron-doped FeSe: Analysis beyond the Migdal-Eliashberg formalism
• Pairing Mechanism of the Heavily Electron Doped FeSe Systems: Dynamical Tuning of the Pairing Cutoff Energy
• Metal-Insulator Transition and Emergent Gapped Phase in the Surface-Doped 2D Semiconductor 2H-MoTe${}_2$
• Evidence for an Additional Symmetry Breaking from Direct Observation of Band Splitting in the Nematic State of FeSe Superconductor
• Electronic Structure of Fe${}_{1.08}$Te bulk crystals and epitaxial FeTe thin films on Bi${}_2$Te${}_3$
• Role of electric fields on enhanced electron correlation in surface-doped FeSe
• Insulating Parent Phase and Distinct Doping Evolution to Superconductivity in Single-Layer FeSe/SrTiO3 Films
• Effect of the sample work function on alkali metal dosing induced electronic structure change
• Direct evidence of a charge depletion region at the interface of Van der Waals monolayers and dielectric oxides: The case of superconducting FeSe/STO
• Enhanced Surface Superconductivity in Ba(Fe${}_{0.95}$Co${}_{0.05}$)${}_2$As${}_2$
• Temperature evolution of the Fermi surface of the FeSe monolayer on SrTiO${}_3$
• What controls the superconducting dome of electron-doped FeSe?