Observation of Discrete Conventional Caroli-de Gennes-Matricon States in the Vortex Core of Single-Layer FeSe/SrTiO_{3}

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

doi:10.1103/PhysRevLett.124.097001

Observation of Discrete Conventional Caroli-de Gennes-Matricon States in the Vortex Core of Single-Layer FeSe/SrTiO_{3}

Phys Rev Lett. 2020 Mar 6;124(9):097001. doi: 10.1103/PhysRevLett.124.097001.

Authors

Chen Chen^{1

2}, Qin Liu^{1

3

2}, Wei-Cheng Bao^{4

5}, Yajun Yan^{1

2}, Qiang-Hua Wang^{4

2}, Tong Zhang^{1

2}, Donglai Feng^{1

2

6}

Affiliations

¹ State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200438, China.
² Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China.
³ Science and Technology on Surface Physics and Chemistry Laboratory, Mianyang, Sichuan 621908, China.
⁴ National Laboratory of Solid State Microstructures & School of Physics, Nanjing University, Nanjing, 210093, China.
⁵ Zhejiang University of Water Resources and Electric Power, Hangzhou 310018, China.
⁶ Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.

PMID: 32202862
DOI: 10.1103/PhysRevLett.124.097001

Abstract

Using low-temperature scanning tunneling microscopy (STM), we studied the vortex states of single-layer FeSe film on a SrTiO_{3} (100) substrate, and the local behaviors of superconductivity at sample boundaries. We clearly observed multiple discrete Caroli-de Gennes-Matricon 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 (±1/2,±3/2,±5/2…) and Δ is the mean superconducting gap over the Fermi surface. Meanwhile, a fully gapped spectrum without states near zero bias is observed at the [110]_{Fe} oriented boundary of 1 and 2 ML FeSe films, and atomic step edge of 1 ML FeSe. Accompanied with theoretical calculations, our results indicate an s-wave pairing without sign change in the high-T_{C} FeSe/SrTiO_{3} superconductor.