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Title: Discovery of orbital-selective Cooper pairing in FeSe

The superconductor iron selenide (FeSe) is of intense interest owing to its unusual nonmagnetic nematic state and potential for high-temperature superconductivity. But its Cooper pairing mechanism has not been determined. Here, we used Bogoliubov quasiparticle interference imaging to determine the Fermi surface geometry of the electronic bands surrounding the Γ = (0,0) and X = (π/a Fe, 0) points of FeSe and to measure the corresponding superconducting energy gaps. We show that both gaps are extremely anisotropic but nodeless and that they exhibit gap maxima oriented orthogonally in momentum space. Moreover, by implementing a novel technique, we demonstrate that these gaps have opposite sign with respect to each other. This complex gap configuration reveals the existence of orbital-selective Cooper pairing that, in FeSe, is based preferentially on electrons from the d yz orbitals of the iron atoms.
Authors:
ORCiD logo [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ; ORCiD logo [7] ;  [8] ; ORCiD logo [9]
  1. Cornell Univ., Ithaca, NY (United States). Lab. of Atomic and Solid State Physics; Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.
  2. Univ. of Copenhagen (Denmark). The Niels Bohr Inst.; Leipzig Univ., Leipzig (Germany). Inst. of Theoretical Physics
  3. Ames Lab., Ames, IA (United States)
  4. Ames Lab., Ames, IA (United States); Univ. of California, Davis, CA (United States). Dept. of Physics
  5. Ames Lab., Ames, IA (United States); Iowa State Univ., Ames, IA (United States). Dept. of Physics and Astronomy
  6. Binghamton Univ., NY (United States). Dept. of Physics; Indian Inst. of Technology (IIT), Madras (India). Dept. of Physics
  7. Univ. of Florida, Gainesville, FL (United States). Dept. of Physics
  8. Univ. of Copenhagen (Denmark). The Niels Bohr Inst.
  9. Cornell Univ., Ithaca, NY (United States). Lab. of Atomic and Solid State Physics; Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.; Univ. of St. Andrews, Scotland (United Kingdom). School of Physics and Astronomy; Univ. College Cork, Cork (Ireland). Tyndall National Inst.
Publication Date:
Report Number(s):
BNL-203333-2018-JAAM
Journal ID: ISSN 0036-8075
Grant/Contract Number:
SC0012704; GBMF4544; GBMF4411; FG02-05ER46236; A9318; AC02-07CH11358; 2009-BNL-PM015
Type:
Accepted Manuscript
Journal Name:
Science
Additional Journal Information:
Journal Volume: 357; Journal Issue: 6346; Journal ID: ISSN 0036-8075
Publisher:
AAAS
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States); Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; Gordon and Betty Moore Foundation; Univ. College Cork, Cork (Ireland); The Lundbeck Foundation; Cornell Univ., Ithaca, NY (United States)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1426451

Sprau, P. O., Kostin, A., Kreisel, A., Böhmer, A. E., Taufour, V., Canfield, P. C., Mukherjee, S., Hirschfeld, P. J., Andersen, B. M., and Davis, J. C. Seamus. Discovery of orbital-selective Cooper pairing in FeSe. United States: N. p., Web. doi:10.1126/science.aal1575.
Sprau, P. O., Kostin, A., Kreisel, A., Böhmer, A. E., Taufour, V., Canfield, P. C., Mukherjee, S., Hirschfeld, P. J., Andersen, B. M., & Davis, J. C. Seamus. Discovery of orbital-selective Cooper pairing in FeSe. United States. doi:10.1126/science.aal1575.
Sprau, P. O., Kostin, A., Kreisel, A., Böhmer, A. E., Taufour, V., Canfield, P. C., Mukherjee, S., Hirschfeld, P. J., Andersen, B. M., and Davis, J. C. Seamus. 2017. "Discovery of orbital-selective Cooper pairing in FeSe". United States. doi:10.1126/science.aal1575. https://www.osti.gov/servlets/purl/1426451.
@article{osti_1426451,
title = {Discovery of orbital-selective Cooper pairing in FeSe},
author = {Sprau, P. O. and Kostin, A. and Kreisel, A. and Böhmer, A. E. and Taufour, V. and Canfield, P. C. and Mukherjee, S. and Hirschfeld, P. J. and Andersen, B. M. and Davis, J. C. Seamus},
abstractNote = {The superconductor iron selenide (FeSe) is of intense interest owing to its unusual nonmagnetic nematic state and potential for high-temperature superconductivity. But its Cooper pairing mechanism has not been determined. Here, we used Bogoliubov quasiparticle interference imaging to determine the Fermi surface geometry of the electronic bands surrounding the Γ = (0,0) and X = (π/aFe, 0) points of FeSe and to measure the corresponding superconducting energy gaps. We show that both gaps are extremely anisotropic but nodeless and that they exhibit gap maxima oriented orthogonally in momentum space. Moreover, by implementing a novel technique, we demonstrate that these gaps have opposite sign with respect to each other. This complex gap configuration reveals the existence of orbital-selective Cooper pairing that, in FeSe, is based preferentially on electrons from the dyz orbitals of the iron atoms.},
doi = {10.1126/science.aal1575},
journal = {Science},
number = 6346,
volume = 357,
place = {United States},
year = {2017},
month = {7}
}

Works referenced in this record:

Imaging Quasiparticle Interference in Bi2Sr2CaCu2O8+δ
journal, July 2002