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Title: Pressure-induced half-collapsed-tetragonal phase in CaKFe 4 As 4

Here, we report the temperature-pressure phase diagram of CaKFe 4As 4 established using high-pressure electrical resistivity, magnetization, and high-energy x-ray diffraction measurements up to 6 GPa. With increasing pressure, both resistivity and magnetization data show that the bulk superconducting transition of CaKFe 4As 4 is suppressed and then disappears at p ≳ 4 GPa. High-pressure x-ray data clearly indicate a phase transition to a collapsed tetragonal phase in CaKFe 4As 4 under pressure that coincides with the abrupt loss of bulk superconductivity near 4 GPa. The x-ray data, combined with resistivity data, indicate that the collapsed tetragonal transition line is essentially independent of pressure, occurring at 4.0(5) GPa for temperatures below 150 K. Density functional theory calculations also find a sudden transition to a collapsed tetragonal state near 4 GPa, as As-As bonding develops across the Ca layer. Bonding across the K layer only occurs for p ≥ 12 GPa. These findings demonstrate a different type of collapsed tetragonal phase in CaKFe 4As 4 as compared to CaFe 2As 2: a half-collapsed tetragonal phase.
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [4] ;  [1] ;  [1] ;  [1] ;  [1] ;  [3] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Ames Lab. and Iowa State Univ., Ames, IA (United States)
  2. Ames Lab. and Iowa State Univ., Ames, IA (United States); Univ. of California, Davis, CA (United States)
  3. Goethe Univ. Frankfurt am Main, Frankfurt am Main (Germany)
  4. Ames Lab. and Iowa State Univ., Ames, IA (United States); Princeton Univ., Princeton, NJ (United States)
Publication Date:
Report Number(s):
IS-J-9469
Journal ID: ISSN 2469-9950; PRBMDO; TRN: US1703266
Grant/Contract Number:
AC02-07CH11358; AC02-06CH11357; SFB/TR49
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 96; Journal Issue: 14; 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
OSTI Identifier:
1406563
Alternate Identifier(s):
OSTI ID: 1395910