Hydrostatic-pressure tuning of magnetic, nonmagnetic, and superconducting states in annealed Ca(Fe1-xCox)(2)As-2

Date
2012-12-01
Authors
Gati, E.
Kohler, S.
Guterding, D.
Wolf, B.
Knoner, S.
Ran, S.
Bud’ko, Sergey
Canfield, Paul
Lang, M.
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Ames Laboratory
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Physics and Astronomy
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Abstract

We report on measurements of the magnetic susceptibility and electrical resistance under He-gas pressure on single crystals of Ca(Fe1−xCox)2As2. We find that for properly heat-treated crystals with modest Co concentration, x = 0.028, the salient ground states associated with iron-arsenide superconductors, i.e., orthorhombic/antiferromagnetic (o/afm), superconducting, and nonmagnetic collapsed-tetragonal (cT) states can be accessed all in one sample with reasonably small and truly hydrostatic pressure. This is possible owing to the extreme sensitivity of the o/afm (for T≤ Ts,N) and superconducting (T≤Tc) states against variation of pressure, disclosing pressure coefficients of dTs,N/dP=−(1100±50) K/GPa and dTc/dP=−(60±3) K/GPa, respectively. Systematic investigations of the various phase transitions and ground states via pressure tuning revealed no coexistence of bulk superconductivity (sc) with the o/afm state which we link to the strongly first-order character of the corresponding structural/magnetic transition in this compound. Our results, together with literature results, indicate that preserving fluctuations associated with the o/afm transition to low enough temperatures is vital for sc to form.

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This article is published as Gati, E., S. Köhler, D. Guterding, B. Wolf, S. Knöner, S. Ran, S. L. Bud'ko, P. C. Canfield, and M. Lang. "Hydrostatic-pressure tuning of magnetic, nonmagnetic, and superconducting states in annealed Ca(Fe1-xCox)(2)As-2." Physical Review B 86, no. 22 (2012): 220511. DOI: 10.1103/PhysRevB.86.220511. Posted with permission.

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