Observation of discrete conventional Caroli-de Gennes-Matricon states in the vortex core of single-layer FeSe/SrTiO3

Abstract

Using low-temperature scanning tunneling microscopy (STM), we studied the vortex states of single-layer FeSe film on SrTiO3 (100) substrate, and the local behaviors of superconductivity at sample boundaries. We clearly observed multiple discrete Caroli-de Gennes-Matricon (CdGM) states in the vortex core, and quantitative analysis shows their energies well follow the formula: E = μΔ^2/E_F, where μ is a half integer and Δ is the mean superconducting gap over the Fermi surface. Meanwhile, a fully gapped spectrum without states near zero bias is observed at [110](Fe) oriented boundary of 1 ML and 2 ML FeSe films, and atomic step edge of 1 ML FeSe. Accompanied with theoretical calculations, our results indicate a s-wave pairing without sign-change in the high-TC FeSe_SrTiO3 superconductor.

arXiv comment10 pages, 5 figures, supplementary materials included

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• Quasi two-dimensional nature of high-Tc superconductivity in iron-based (Li,Fe)OHFeSe
• Evidence of zero point fluctuation of vortices in a very weakly pinned a-MoGe thin film
• Revealing the Microscopic Mechanism of Elementary Vortex Pinning in Superconductors
• Competing energy scales in topological superconducting heterostructures
• Unveiling non-Abelian statistics of vortex Majorana bound states in iron-based superconductors using fermionic modes
• Stoichiometric FeTe is a Superconductor
• Necklace-like pattern of vortex bound states
• Caroli-de Gennes-Matricon Analogs in Full-Shell Hybrid Nanowires
• Large spectral gap and impurity-induced states in a two-dimensional Abrikosov vortex
• Capping layer influence and isotropic in-plane upper critical field of the superconductivity at the FeSe/SrTiO3 interface
• Quantum Mechanics of an Abrikosov Vortex in Nanofabricated Pinning Potential