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Title: Enhancement of superconducting transition temperature by pointlike disorder and anisotropic energy gap in FeSe single crystals

A highly anisotropic superconducting gap is found in single crystals of FeSe by studying the London penetration depth Δλ measured down to 50 mK in samples before and after 2.5 MeV electron irradiation. The gap minimum increases with introduced pointlike disorder, indicating the absence of symmetry-imposed nodes. Surprisingly, the superconducting transition temperature Tc increases by 0.4 K from Tc0 ≈ 8.8 K while the structural transition temperature Ts decreases by 0.9 K from Ts0 ≈ 91.2 K after electron irradiation. Finally, we discuss several explanations for the Tc enhancement and propose that local strengthening of the pair interaction by irradiation-induced Frenkel defects most likely explains the phenomenon.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [1] ;  [1] ;  [1]
  1. Ames Lab. and Iowa State Univ., Ames, IA (United States)
  2. Univ. Paris-Saclay, Palaiseau Cedex (France)
  3. Univ. of Tennessee, Knoxville, TN (United States)
  4. Univ. of Florida, Gainesville, FL (United States)
Publication Date:
OSTI Identifier:
1350069
Report Number(s):
IS-J-9233
Journal ID: ISSN 2469-9950; PRBMDO
Grant/Contract Number:
AC02-07CH11358; NSF-DMR-1407502; PD-226
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 94; Journal Issue: 6; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Ames Laboratory (AMES), Ames, IA (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