Scrutinizing the double superconducting gaps and strong coupling pairing in (Li1-xFexOH)FeSe

Abstract

In the iron based superconductors, one of the on-going frontier studies is about the pairing mechanism. The recent interest concerns the high temperature superconductivity and its intimate reason in the monolayer FeSe thin films. The challenge here is how the double superconducting gaps seen by the scanning tunnelling spectroscopy (STS) associate however to only one set of Fermi pockets seen by the angle resolved photoemission spectroscopy (ARPES). The recently discovered (Li1-xFexOH)FeSe phase with Tc=40 K provides a good platform to check the fundamental problems. Here we report the STS study on the (Li1-xFexOH)FeSe single crystals. The STS spectrum clearly indicates the presence of double anisotropic gaps with maximum magnitudes of Delta_1=14.3 meV and Delta_2=8.6 meV, and mimics that of the monolayer FeSe thin film. Further analysis based on the quasiparticle interference (QPI) allows us to rule out the d-wave gap, and for the first time assign the larger (smaller) gap to the outer (inner) hybridized Fermi pockets associating with the dxy (dxz/dyz) orbitals, respectively. The huge value Delta_1/k_BT_c = 8.7 discovered here undoubtedly proves the strong coupling mechanism in the present superconducting system.

24 pages, 10 figures, with the Supplementary Information. The second version supersedes the original version with detailed QPI data and analysis

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Cited by in corpus (50)

• Robust and clean Majorana zero mode in the vortex core of high-temperature superconductor (Li0.84Fe0.16)OHFeSe
• Common Electronic Origin of Superconductivity in (Li,Fe)OHFeSe Bulk Superconductor and Single-Layer FeSe/SrTiO3 Films
• Monolayer FeSe on SrTiO${}_3$
• On the Remarkable Superconductivity of FeSe and its Close Cousins
• Observation of Double-Dome Superconductivity in Potassium-Doped FeSe Thin Films
• Preformed Cooper pairs in layered FeSe-based superconductors
• Experimental Demonstration of the Sign Reversal of the Order Parameter in (Li1-xFex)OHFe1-yZnySe
• Reemergence of high-Tc superconductivity in the (Li1-xFex)OHFe1-ySe under high pressure
• Interface high-temperature superconductivity
• Resilient nodeless $d$-wave superconductivity in monolayer FeSe
• Multi-band superconductivity and large anisotropy in FeS crystals
• Superconductivity in FeSe thin films driven by the interplay between nematic fluctuations and spin-orbit coupling
• Surface electronic structure and evidence of plain s-wave superconductivity in (Li0.8Fe0.2)OHFeSe
• Superconductivity across Lifshitz transition and anomalous insulating state in surface K-dosed (Li0.8Fe0.2OH)FeSe
• Dumbbell Defects in FeSe Films: A Scanning Tunneling Microscopy and First-Principles Investigation
• Odd and even modes of neutron spin resonance in the bilayer iron-based superconductor CaKFe${}_4$As${}_4$
• Structure of spin excitations in heavily electron-doped Li0.8Fe0.2ODFeSe superconductors
• Proximity induced superconductivity within the insulating (Li${}_{0.84}$Fe${}_{0.16}$)OH layers in (Li${}_{0.84}$Fe${}_{0.16}$)OHFe${}_{0.98}$Se
• Unconventional density waves and superconductivities in Fe-based superconductors and other strongly correlated electron systems
• Superconductivity without hole-pocket in electron-doped FeSe: Analysis beyond the Migdal-Eliashberg formalism
• Classification of Symmetry Derived Pairing at M Point in FeSe
• Spin resonance in the superconducting state of Li${}_{1-x}$Fe${}_x$ODFe${}_{1-y}$Se observed by neutron spectroscopy
• Single particle tunneling spectroscopy and superconducting gaps in layered iron based superconductor KCa${}_2$Fe${}_4$As${}_4$F${}_2$
• Low-energy spin excitations in Li(0.8)Fe(0.2)ODFeSe superconductor studied with inelastic neutron scattering
• Direct visualization of sign reversal s^+- superconducting gaps in FeTe0.55Se0.45
• Synthesis, phase stability, structural and physical properties of 11-type iron chalcogenides
• Ab-initio Studies of (Li${}_{0.8}$Fe${}_{0.2}$)OHFeSe Superconductors: Revealing the Dual Roles of Fe${}_{0.2}$ in Structural Stability and Charge Transfer
• Raman Study of Cooper Pairing Instabilities in (Li${}_{1-x}$Fe${}_x$)OHFeSe
• Shortcuts to Adiabaticity Assisted by Counterdiabatic Born-Oppenheimer Dynamics
• Charge order driven by multiple-Q spin fluctuations in heavily electron-doped iron selenide superconductors
• Twofold symmetry of proximity-induced superconductivity in Bi${}_2$Te${}_3$/Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$ heterostructures revealed by scanning tunneling microscopy
• Sign reversal superconducting gaps revealed by phase referenced quasi-particle interference of impurity induced bound states in (Li${}_{1-x}$Fe${}_x$)OHFe${}_{1-y}$Zn${}_y$Se
• ARPES Detection of Superconducting Gap Sign in Unconventional Superconductors
• Observation of superconducting pair density modulation within lattice unit cell
• Probing the superconducting gap structure of (Li${}_{1-x}$Fe${}_x$)OHFeSe
• Possible spin excitation structure in monolayer FeSe grown on SrTiO${}_3$
• Phase shift and magnetic anisotropy induced field splitting of impurity states in (Li1-xFex)OHFeSe superconductor
• Doping Mn into (Li1-xFex)OHFe1-ySe superconducting crystals via ion-exchange and ion-release/introduction syntheses
• Orbital-Selective High-Temperature Cooper Pairing Developed in the Two-Dimensional Limit
• Many-body physics-induced selection rules: application to Raman spectroscopy
• Theory Perspective: SCES 2016
• Multi-Atom Quasiparticle Scattering Interference for Superconductor Energy-Gap Symmetry Determination
• Doping effects on electronic states in electron-doped FeSe: Impact of self-energy and vertex corrections
• Anisotropic gap structure and sign reversal symmetry in monolayer Fe(Se,Te)
• Long range magnetic order in hydroxide layer doped (Li${}_{1-x-y}$Fe${}_x$Mn${}_y$OD)FeSe
• Equally Spaced Quantum States in van der Waals Epitaxy-Grown Nanoislands
• Nodeless multigap superconductivity in organic-ion-intercalated (tetrabutyl~ammonium)${}_{0.3}$FeSe
• Spin correlations in the parent phase of Li${}_{1-x}$Fe${}_x$ODFeSe
• Moire Engineering of Cooper-Pair Density Modulation States
• Electronic and Superconducting Properties of Some FeSe-based Single Crystals and Films Grown Hydrothermally