Interface enhanced superconductivity in monolayer FeSe films on MgO(001):charge transfer with atomic substitution  

作　　者：Guanyu Zhou Qinghua Zhang Fawei Zheng Ding Zhang Chong Liu Xiaoxiao Wang Can-Li Song Ke He Xu-Cun Ma Lin Gu Ping Zhang Lili Wang Qi-Kun Xue 

机构地区：[1]State Key Laboratory of Low-Dimensional Quantum Physics,Department of Physics,Tsinghua University,Beijing 100084,China [2]Laboratory for Advanced Materials&Electron Microscopy,Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China [3]Institute of Applied Physics and Computational Mathematics,Beijing 100088,China [4]Collaborative Innovation Center of Quantum Matter,Beijing 100084,China

出　　处：《Science Bulletin》2018年第12期747-752,共6页科学通报（英文版）

基　　金：supported by the National Natural Science Foundation of China(11574174,11774193,11790311,11404183,11474030,21573121 and 51421002);the National Basic Research Program of China(2015CB921000);the President Foundation of China Academy of Engineering Physics(YZJJLX2016010);the Strategic Priority Research Program of Chinese Academy of Sciences(XDB07030200)

摘　　要：Interface enhanced superconductivity over 50 K has been discovered in monolayer Fe Se films grown on several TiO_2-terminated oxide substrates.Whether such phenomenon exists in other oxide substrates remains an extremely interesting topic.Here we report enhanced superconductivity with an onset transition temperature of 18 K in monolayer Fe Se on Mg O(001) substrate by transport measurement.Scanning transmission electron microscopy investigation on the interface structure indicates that Fe Se films grow epitaxially on Mg O(001) and that overlayer Fe atoms diffuse into the top two layers of Mg O and substitute Mg atoms.Our density functional theory calculations reveal that this substitution promotes the charge transfer from the Mg O substrate to the Fe Se films,an essential process that also occurs in monolayer Fe Se on TiO_2-terminated oxides and contributes to the enhanced superconductivity therein.Our finding suggests that superconductivity enhancement in monolayer Fe Se films on oxides substrates is rather general as long as charge transfer is allowed at the interface,thus pointing out an explicit direction for searching for new high temperature superconductivity by interface engineering.Interface enhanced superconductivity over 50 K has been discovered in monolayer FeSe films grown on several TiO2-terminated oxide substrates. Whether such phenomenon exists in other oxide substrates remains an extremely interesting topic. Here we report enhanced superconductivity with an onset tran- sition temperature of 18 K in monolayer FeSe on MgO（001） substrate by transport measurement. Scanning transmission electron microscopy investigation on the interface structure indicates that FeSe films grow epitaxially on MgO（001） and that overlayer Fe atoms diffuse into the top two layers of MgO and substitute Mg atoms. Our density functional theory calculations reveal that this substitution promotes the charge transfer from the MgO substrate to the FeSe films, an essential process that also occurs in monolayer FeSe on TiO2-terminated oxides and contributes to the enhanced superconductivity therein. Our finding suggests that superconductivity enhancement in monolayer FeSe films on oxides substrates is rather general as long as charge transfer is allowed at the interface, thus pointing out an explicit direction for searching for new high temperature superconductivity by interface engineering.

关 键 词：FeSe/MgO interface Interface superconductivity Transport measurement Scanning transmission electron microscopy 

分 类 号：O511[理学—低温物理]