Lithium impurity induced electron doping and in-gap states in high-<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>T</mi><mi>c</mi></msub></math> monolayer <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi>Fe</mi><mo>(</mo><mi>Te</mi><mo>,</mo><mi>Se</mi><mo>)</mo><mo>/</mo><mi>SrTiO</mi></mrow><mn>3</mn></msub></math>

Yuxuan Lei; Zhuoran Xu; Guanyang He; Yu Li; Yi Liu; Yanzhao Liu; Jian Wang

doi:10.1103/b2yd-5q73

Lithium impurity induced electron doping and in-gap states in high- $T_{c}$ monolayer ${Fe (Te, Se) / SrTiO}_{3}$

Yuxuan Lei ^1,2, Zhuoran Xu ^1,3, Guanyang He ^1,4, Yu Li¹, Yi Liu^5,6,*, Yanzhao Liu^7,†, and Jian Wang ^1,2,3,8,‡

¹International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
²Beijing Academy of Quantum Information Sciences, Beijing 100193, China
³Hefei National Laboratory, Hefei 230088, China
⁴ShanghaiTech Laboratory for Topological Physics, ShanghaiTech University, Shanghai 201210, China
⁵School of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China
⁶Key Laboratory of Quantum State Construction and Manipulation (Ministry of Education), Renmin University of China, Beijing 100872, China
⁷Quantum Science Center of Guangdong–Hong Kong–Macao Greater Bay Area (Guangdong), Shenzhen 518045, China
⁸Collaborative Innovation Center of Quantum Matter, Beijing 100871, China

^*Contact author: yiliu@ruc.edu.cn
^†Contact author: liuyanzhao@quantumsc.cn
^‡Contact author: jianwangphysics@pku.edu.cn

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Phys. Rev. B 113, 014512 – Published 20 January, 2026

DOI: https://doi.org/10.1103/b2yd-5q73

Abstract

Monolayer Fe(Te,Se) film grown on $SrTi O_{3}$ (STO) substrate has attracted considerable interest due to its interface-enhanced high-temperature (high- $T_{c}$ ) superconductivity and potential topological electronic properties. While electron doping is widely considered a key factor in enhancing superconductivity, experimental studies on its effects in monolayer Fe(Te,Se)/STO systems remain limited. In this work, utilizing scanning tunneling microscopy/spectroscopy and quasiparticle interference method, we investigated the modulation of the electronic structure and superconductivity of monolayer Fe(Te,Se)/STO induced by the lithium-impurities-induced electron doping. After depositing lithium clusters of varying sizes on the film surface, we detected the reduction of the effective mass and suppressed superconductivity, which can be attributed to the excessive electron doping. Besides, in-gap bound states induced by nonmagnetic lithium clusters were observed, supporting sign-reversing pairing symmetry. These findings demonstrate how electronic structure and superconductivity in monolayer Fe(Te,Se) film respond to electron doping and local impurities, which provides evidence of the unconventional pairing in monolayer Fe(Te,Se) film, offers insights for studying the iron-based high- $T_{c}$ superconductivity.

Physical Review B

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Lithium impurity induced electron doping and in-gap states in high- $T_{c}$ monolayer ${Fe (Te, Se) / SrTiO}_{3}$

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Lithium impurity induced electron doping and in-gap states in high-Tc monolayer Fe(Te,Se)/SrTiO3

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Lithium impurity induced electron doping and in-gap states in high- $T_{c}$ monolayer ${Fe (Te, Se) / SrTiO}_{3}$