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

Chen Chen; Qin Liu; Wei-Cheng Bao; Yajun Yan; Qiang-Hua Wang; Tong Zhang; Donglai Feng

doi:10.1103/physrevlett.124.097001

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arXiv · 1905.01850

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

Chen Chen·Qin Liu·Wei-Cheng Bao·Yajun Yan·Qiang-Hua Wang·Tong Zhang·Donglai Feng

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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.

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Chen Chen, Qin Liu, Wei-Cheng Bao, Yajun Yan, Qiang-Hua Wang, Tong Zhang, Donglai Feng. 2020-02-16. Observation of discrete conventional Caroli-de Gennes-Matricon states in the vortex core of single-layer FeSe/SrTiO3. https://doi.org/10.1103/physrevlett.124.097001

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