Direct visualization of sign reversal s^+- superconducting gaps in FeTe0.55Se0.45

Abstract

In many unconventional superconductors, the pairing of electrons is driven by the repulsive interaction, which leads to the sign reversal of superconducting gaps along the Fermi surfaces (FS) or between them. However, to measure this sign change is not easy and straightforward. It is known that, in superconductors with sign reversal gaps, non-magnetic impurities can break Cooper pairs leading to the quasiparticle density of states in the superconducting state. The standing waves of these quasiparticles will interfere each other leading to the quasiparticle interference (QPI) pattern which carries the phase message reflecting also the superconducting gap structure. Based on the recently proposed defect-bound-state QPI technique, we explore the applicability of this technique to a typical iron based superconductor FeTe${}_{0.55}$Se${}_{0.45}$ with roughly equivalent gap values on the electron and hole pockets connected by the wave vector q_2=(0,π). It is found that, on the negative energy side, with the energy slightly below the gap value, the phase reference quantity $|g(q,-E)|\cos(θ_{q,+E}-θ_{q,-E}) becomes negative and the amplitude is strongly enhanced with the scattering vector q_2, but that corresponding to the scattering between the electron-electron pockets, namely q_3=(π,π), keeps all positive. This is well consistent with the theoretical expectation of the s^+- pairing gap and thus serves as a direct visualization of the sign reversal gaps. This experimental observation is also supported by the theoretical calculations with the Fermi surface structure and s^+- pairing gap.

arXiv comment10 pages, 6 figures

References in corpus (28)

• Unconventional sign-reversing superconductivity in LaFeAsO_(1-x)F_x
• Unconventional pairing originating from disconnected Fermi surfaces in superconducting LaFeAsO${}_{1-x}$F${}_x$}
• Gap symmetry and structure of Fe-based superconductors
• Resonant Spin Excitation in the High Temperature Superconductor Ba0.6K0.4Fe2As2
• Reply to Comment on "Unconventional s-wave superconductivity in Fe(Se,Te)"
• Discovery of Orbital-Selective Cooper Pairing in FeSe
• Observation of a Robust Zero-energy Bound State in Iron-based Superconductor Fe(Te,Se)
• Spectroscopic scanning tunneling microscopy insights into Fe-based superconductors
• Anisotropic Energy Gaps of Iron-based Superconductivity from Intra-band Quasiparticle Interference in LiFeAs
• Shallow pockets and very strong coupling superconductivity in FeSe_xTe_1-x
• Isotropic superconducting gaps with enhanced pairing on electron Fermi surfaces in FeTe0.55Se0.45
• Discrete energy levels of Caroli-de Gennes-Martricon states in quantum limit due to small Fermi energy in FeTe${}_{0.55}$Se${}_{0.45}$
• Scrutinizing the double superconducting gaps and strong coupling pairing in (Li1-xFexOH)FeSe
• Experimental Demonstration of the Sign Reversal of the Order Parameter in (Li1-xFex)OHFe1-yZnySe
• Probing the Unconventional Superconducting State of LiFeAs by Quasiparticle Interference
• Close relationship between superconductivity and the bosonic mode in Ba0.6K0.4Fe2As2 and Na(Fe0.975Co0.025)As
• Possible phase-sensitive tests of pairing symmetry in pnictide superconductors
• Experimental Observation of Incoherent-Coherent Crossover and Orbital Dependent Band Renormalization in Iron Chalcogenide Superconductors
• Quasiparticle Scattering Interference in Superconducting Iron-pnictides
• Sign inversion in the superconducting order parameter of LiFeAs inferred from Bogoliubov quasiparticle interference
• In-Gap Quasiparticle Excitations Induced by Non-Magnetic Cu Impurities in Na(Fe0.96Co0.03Cu0.01)As Revealed by Scanning Tunneling Spectroscopy
• Single Impurity Problem in Iron-Pnictide Superconductors
• Quasiparticle interference in an iron-based superconductor
• Robustness of Quasiparticle Interference Test for Sign-changing Gaps in Multiband Superconductors
• 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
• Determination of the Superconducting Order Parameter from Defect Bound State Quasiparticle Interference
• Extracting phase information about the superconducting order parameter from defect bound states
• Tuning across the BCS-BEC crossover in the multiband superconductor Fe${}_{1+y}$Se${}_x$Te${}_{1-x}$ : An angle-resolved photoemission study

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