单层FeSe薄膜/氧化物界面高温超导

丁翠; 刘充; 张庆华; 龚冠铭; 汪恒; 刘效治; 孟繁琦; 杨好好; 武睿; 宋灿立; 李渭; 何珂; 马旭村; 谷林; 王立莉; 薛其坤

doi:10.7498/aps.67.20181681

摘要

单层FeSe/SrTiO3界面增强超导的发现为理解高温超导机理提供了一个新的途径，也为实现新的高温超导体开拓了新思路.本文通过在SrTiO3（001）表面高温沉积Mg进而沉积单层FeSe薄膜，制备出了FeSe/MgO双层/SrTiO3异质结.利用扫描隧道显微镜研究了异质结的电学及超导特性，观测到约1415 meV的超导能隙，比体相FeSe超导能隙值增大了56倍，与K掺杂双层FeSe/SrTiO3的超导能隙值相当.这一结果可理解为能带弯曲造成的界面电荷转移和界面处电声耦合共同作用导致的超导增强.FeSe/MgO界面是继FeSe/TiO2之后的一个新界面超导体系，为研究界面高温超导机理提供了新载体.

关键词:

Abstract

We report on the observation of a superconducting gap of about 14-15 meV, significantly enlarged compared with the value of 2.2 meV for bulk FeSe, in monolayer FeSe film interfaced with MgO epitaxial on SrTiO3(001) substrate by using the scanning tunneling microscopy. While the MgO exhibits the same work function as SrTiO3 substrate, the gap magnitude is in coincidence with that of surface K-doped two-unit-cell FeSe film on SrTiO3(001), suggesting that the interface enhanced superconductivity might be attributed to cooperation of interface charge transfer driven by band bending with interface electron-phonon coupling as discovered at FeSe/TiO2 interfaces. On the other hand, the observation of such an enlarged superconducting gap, complementary to our previous transport observation of an onset superconducting transition temperature of 18 K in monolayer FeSe film on a bulk MgO substrate, implies that FeSe/MgO interface is likely to be a new interface high-temperature superconducting system, providing a new platform for investigating the mechanism of interface hightemperature superconductivity.

Keywords:

FeSe/MgO /
interface enhanced superconductivity /
scanning tunneling microscopy /
scanning transmission electron microscopy

作者及机构信息

1.
清华大学物理系, 低维量子物理国家重点实验室, 北京 100084;

2.
中国科学院物理研究所, 先进材料与结构分析实验室, 北京凝聚态物理国家研究中心, 北京 100190;

3.
量子物质科学协同创新中心, 北京 100084

通信作者: 王立莉, liliwang@mail.tsinghua.edu.cn;qkxue@mail.tsinghua.edu.cn ; 薛其坤, liliwang@mail.tsinghua.edu.cn;qkxue@mail.tsinghua.edu.cn

基金项目: 国家自然科学基金（批准号：11574174，11774193，11790311，51522212，51421002，51672307）、国家重点基础研究发展计划（批准号：2015CB921000，2014CB921002）和中国科学院战略优先研究项目（批准号：XDB07030200）资助的课题.

Authors and contacts

1.
State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China;

2.
Beijing National Laboratory for Condensed Matter Physics, Laboratory for Advanced Materials and Electron Microscopy, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;

3.
Collaborative Innovation Center of Quantum Matter, Beijing 100084, China

Corresponding author: Wang Li-Li, liliwang@mail.tsinghua.edu.cn;qkxue@mail.tsinghua.edu.cn ; Xue Qi-Kun, liliwang@mail.tsinghua.edu.cn;qkxue@mail.tsinghua.edu.cn

Funds: Project supported by the National Natural Science Foundation of China (Grant Nos. 11574174, 11774193, 11790311, 51522212, 51421002, 51672307), the National Basic Research Program of China (Grant Nos. 2015CB921000, 2014CB921002), and the Strategic Priority Research Program of the Chinese Academy of Sciences, China (Grant No. XDB07030200).

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施引文献

[1]	Wang Q Y, Li Z, Zhang W H, et al. 2012 Chin. Phys. Lett. 29 037402
[2]	Song C L, Wang Y L, Cheng P, et al. 2011 Science 332 1410
[3]	Zhang W H, Sun Y, Zhang J S, et al. 2014 Chin. Phys. Lett. 31 017401
[4]	Zhang Z, Wang Y H, Song Q, et al. 2015 Sci. Bull. 60 1301
[5]	Ge J F, Liu Z L, Liu C, et al. 2015 Nat. Mater. 14 285
[6]	Peng R, Xu H C, Tan S Y, et al. 2014 Nat. Commun. 5 5044
[7]	Zhou G, Zhang D, Liu C, et al. 2016 Appl. Phys. Lett. 108 202603
[8]	Zhang P, Peng X L, Qian T, et al. 2016 Phys. Rev. B 94 104510
[9]	Zhang C, Liu Z, Chen Z, et al. 2017 Nat. Commun. 8 14468
[10]	Ding H, Lv Y F, Zhao K, et al. 2016 Phys. Rev. Lett. 117 067001
[11]	Rebec S N, Jia T, Zhang C, et al. 2017 Phys. Rev. Lett. 118 067002
[12]	Wang L, Ma X C, Xue Q K 2016 Supercond. Sci. Technol. 29 123001
[13]	Wang L, Xue Q K 2017 AAPPS Bull. 27 4
[14]	Maletz J, Zabolotnnyy V B, Evtushinsky D V, et al. 2014 Phys. Rev. B 89 220506(R)
[15]	He S, He J, Zhang W, et al. 2013 Nat. Mater. 12 605
[16]	Tan S, Zhang Y, Xia M, et al. 2013 Nat. Mater. 12 634
[17]	Lee J J, Schmitt F T, Moore R G, et al. 2014 Nature 515 245
[18]	Song C L, Zhang H M, Zhong Y, et al. 2016 Phys. Rev. Lett. 116 157001
[19]	Guo J, Jin S, Wang G, et al. 2010 Phys. Rev. B 82 180520
[20]	Lu X F, Wang N Z, Wu H, et al. 2015 Nat. Mater. 14 325
[21]	Shiogai J, Ito Y, Mitsuhashi T, et al. 2015 Nat. Phys. 12 42
[22]	Lei B, Cui J H, Xiang Z J, et al. 2016 Phys. Rev. Lett. 116 077002
[23]	Hanzawa K, Sato H, Hiramatsu H, et al. 2016 Proc. Natl. Acad. Sci. U.S.A. 113 3986
[24]	Zhang S, Guan J, Jia X, et al. 2016 Phys. Rev. B 94 081116
[25]	Zhang H, Zhang D, Lu X, et al. 2017 Nat. Commun. 8 214
[26]	Tang C, Liu C, Zhou G, et al. 2016 Phys. Rev. B 93 020507
[27]	Zhang W H, Liu X, Wen C H, et al. 2016 Nano Lett. 16 1969
[28]	Xie Y, Cao H Y, Zhou Y, et al. 2015 Sci. Rep. 5 10011
[29]	Wang Y, Linscheid A, Berlijn T, et al. 2016 Phys. Rev. B 93 134513
[30]	Li Z X, Wang F, Yao H, et al. 2016 Sci. Bull. 61 925
[31]	Lee D H 2018 Ann. Rev. Conden. Matter Phys. 9 261
[32]	Chu C W, Deng L Z, Lv B 2015 Physica C 514 290
[33]	Kamihara Y, Watanabe T, Hirano M, et al. 2008 J. Am. Chem. Soc. 130 3296
[34]	Ren Z, Lu W, Yang J, et al. 2008 Chin. Phys. Lett. 25 2215
[35]	Dingle R, Stormer H L, Gossard A C, Wiegmann W 1978 Appl. Phys. Lett. 33 665
[36]	Zhou G, Zhang Q, Zheng F, et al. 2018 Sci. Bull. 63 747
[37]	Binnig G, Rohrer H 1983 Surf. Sci. 126 236
[38]	Lim J Y, Oh J S, Ko B D, et al. 2003 J. Appl. Phys. 94 764
[39]	Susaki T, Shigaki N, Matsuzaki K, et al. 2014 Phys. Rev. B 90 035453
[40]	Li F, Zhang Q, Tang C, et al. 2016 2D Mater. 3 024002
[41]	Choubey P, Berlijn T, Kreisel A, et al. 2014 Phys. Rev. B 90 134520
[42]	Liu C, Mao J, Ding H, et al. 2018 Phys. Rev. B 97 024502
[43]	Zhang W, Li Z, Li F, et al. 2014 Phys. Rev. B 89 060506
[44]	Parlinski K, Łazewski J, Kawazoe Y 2000 J. Phys. Chem. Solids 61 87
[45]	Wang Y, Liu Z K, Chen L Q, et al. 2006 J. Appl. Phys. 100 023533
[46]	Oshima C, Aizawa T, Souda R, et al. 1990 Solid State Commun. 73 731
[47]	Coh S, Lee D H, Louie S G, et al. 2016 Phys. Rev. B 93 245138
[48]	Niu F, Meier A L, Wessels B W 2006 J. Vac. Sci. Technol. B 24 2586

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