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Title: Superconductivity below 20 K in heavily electron-doped surface layer of FeSe bulk crystal

A superconducting transition temperature (T c ) as high as 100 K was recently discovered in one monolayer FeSe grown on SrTiO 3 . The discovery ignited efforts to identify the mechanism for the markedly enhanced T c from its bulk value of 8 K. There are two main views about the origin of the T c enhancement: interfacial effects and/or excess electrons with strong electron correlation. Here, we report the observation of superconductivity below 20 K in surface electron-doped bulk FeSe. The doped surface layer possesses all the key spectroscopic aspects of the monolayer FeSe on SrTiO 3 . Without interfacial effects, the surface layer state has a moderate T c of 20 K with a smaller gap opening of 4.2 meV. Our results show that excess electrons with strong correlation cannot induce the maximum T c , which in turn reveals the need for interfacial effects to achieve the highest T c in one monolayer FeSe on SrTiO 3 .
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [5] ;  [6] ;  [6] ;  [3] ;  [7]
  1. Yonsei Univ., Seoul (Korea). Inst. of Physics and Applied Physics; Inst. for Basic Science, Seoul (Korea). Center for Correlated Electron Systems
  2. Pohang Univ. of Science and Technology (POSTECH) (Korea, Republic of). Dept. of Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source
  3. Inst. for Basic Science, Seoul (Korea). Center for Correlated Electron Systems; Seoul National Univ. (Korea, Republic of). Dept. of Physics and Astronomy
  4. Yonsei Univ., Seoul (Korea). Inst. of Physics and Applied Physics
  5. Pohang Univ. of Science and Technology (POSTECH) (Korea, Republic of). Dept. of Physics
  6. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source
  7. Inst. for Basic Science, Seoul (Korea). Center for Correlated Electron Systems; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source; Seoul National Univ. (Korea, Republic of). Dept. of Physics and Astronomy
Publication Date:
Grant/Contract Number:
AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 7; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; electronic properties and materials; superconducting properties and materials
OSTI Identifier:
1379279