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Title: Combined effects of Sr substitution and pressure on the ground states in CaFe 2 As 2

Here, we present a detailed study of the combined effects of Sr substitution and hydrostatic pressure on the ground-state properties of CaFe 2As 2. Measurements of the electrical resistance and magnetic susceptibility, both at ambient and finite pressure P ≤ 2 GPa, were performed on Ca 1–xSr xFe 2As 2 single crystals grown out of Sn flux. We find that by Sr substitution the transition temperature to the magnetic/structural phase is enhanced and therefore a higher pressure is needed to suppress the transition to lowest temperature. In addition, the transition to the collapsed tetragonal phase is found at a pressure, which is distinctly higher than in the pure compound. This implies that the stability ranges of both phases shift on the pressure-axis upon doping, but the latter one with a higher rate. These observations suggest the possibility of separating the two phase lines, which intersect already at elevated temperatures for x = 0 and low Sr concentration levels. For x = 0.177, we find strong evidence that both phases remain separated down to the lowest temperature and that a zero-resistance state emerges in this intermediate pressure window. This observation indicates that Sr substitution combined with hydrostatic pressure provides another routemore » for stabilizing superconductivity in CaFe 2As 2. Lastly, our results are consistent with the notion that (i) preserving the fluctuations associated with the structural-magnetic transition to low temperatures is vital for superconductivity to form in this material and that (ii) the nonmagnetic collapsed tetragonal phase is detrimental for superconductivity.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [4] ;  [1]
  1. J.W. Goethe-Univ. Frankfurt(M), Frankfurt(M) (Germany)
  2. Ames Lab. and Iowa State Univ., Ames, IA (United States); Univ. of California, San Diego, CA (United States)
  3. San Diego State Univ., San Diego, CA (United States)
  4. Ames Lab. and Iowa State Univ., Ames, IA (United States)
Publication Date:
Report Number(s):
IS-J-9130
Journal ID: ISSN 2469-9950; PRBMDO
Grant/Contract Number:
AC02-07CH11358
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 94; 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:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
OSTI Identifier:
1335025
Alternate Identifier(s):
OSTI ID: 1329508

Knoner, S., Gati, E., Kohler, S., Wolf, B., Tutsch, U., Ran, S., Torikachvili, M. S., Bud'ko, S. L., Canfield, P. C., and Lang, M.. Combined effects of Sr substitution and pressure on the ground states in CaFe2As2. United States: N. p., Web. doi:10.1103/PhysRevB.94.144513.
Knoner, S., Gati, E., Kohler, S., Wolf, B., Tutsch, U., Ran, S., Torikachvili, M. S., Bud'ko, S. L., Canfield, P. C., & Lang, M.. Combined effects of Sr substitution and pressure on the ground states in CaFe2As2. United States. doi:10.1103/PhysRevB.94.144513.
Knoner, S., Gati, E., Kohler, S., Wolf, B., Tutsch, U., Ran, S., Torikachvili, M. S., Bud'ko, S. L., Canfield, P. C., and Lang, M.. 2016. "Combined effects of Sr substitution and pressure on the ground states in CaFe2As2". United States. doi:10.1103/PhysRevB.94.144513. https://www.osti.gov/servlets/purl/1335025.
@article{osti_1335025,
title = {Combined effects of Sr substitution and pressure on the ground states in CaFe2As2},
author = {Knoner, S. and Gati, E. and Kohler, S. and Wolf, B. and Tutsch, U. and Ran, S. and Torikachvili, M. S. and Bud'ko, S. L. and Canfield, P. C. and Lang, M.},
abstractNote = {Here, we present a detailed study of the combined effects of Sr substitution and hydrostatic pressure on the ground-state properties of CaFe2As2. Measurements of the electrical resistance and magnetic susceptibility, both at ambient and finite pressure P ≤ 2 GPa, were performed on Ca1–xSrxFe2As2 single crystals grown out of Sn flux. We find that by Sr substitution the transition temperature to the magnetic/structural phase is enhanced and therefore a higher pressure is needed to suppress the transition to lowest temperature. In addition, the transition to the collapsed tetragonal phase is found at a pressure, which is distinctly higher than in the pure compound. This implies that the stability ranges of both phases shift on the pressure-axis upon doping, but the latter one with a higher rate. These observations suggest the possibility of separating the two phase lines, which intersect already at elevated temperatures for x = 0 and low Sr concentration levels. For x = 0.177, we find strong evidence that both phases remain separated down to the lowest temperature and that a zero-resistance state emerges in this intermediate pressure window. This observation indicates that Sr substitution combined with hydrostatic pressure provides another route for stabilizing superconductivity in CaFe2As2. Lastly, our results are consistent with the notion that (i) preserving the fluctuations associated with the structural-magnetic transition to low temperatures is vital for superconductivity to form in this material and that (ii) the nonmagnetic collapsed tetragonal phase is detrimental for superconductivity.},
doi = {10.1103/PhysRevB.94.144513},
journal = {Physical Review B},
number = 14,
volume = 94,
place = {United States},
year = {2016},
month = {10}
}