Specific heat and upper critical fields in KFe2As2 single crystals

M. Abdel-Hafiez, S. Aswartham, S. Wurmehl, V. Grinenko, C. Hess, S.-L. Drechsler, S. Johnston, A. U. B. Wolter, B. Büchner, H. Rosner, and L. Boeri
Phys. Rev. B 85, 134533 – Published 30 April 2012; Erratum Phys. Rev. B 85, 179901 (2012)

Abstract

We report low-temperature specific heat measurements for high-quality single crystalline KFe2As2 (Tc3.5 K). The investigated zero-field specific heat data yields an unusually large nominal Sommerfeld coefficient, γn=94(3) mJ/mol K2, which is, however, affected by extrinsic contributions as evidenced by a sizable residual linear specific heat and various theoretical considerations, including an analysis of Kadowaki-Woods relations. These results indicate that KFe2As2 should be classified as a weakly or intermediately coupled superconductor with a total electron-boson coupling constant λtot1 (including a calculated weak electron-phonon coupling λph=0.17). From specific heat and ac susceptibility studies in external magnetic fields the magnetic phase diagram is also constructed. We confirm the high anisotropy of the upper critical fields μ0Hc2(T), ranging from a factor of 5 near Tc to a slightly reduced value around 4.5 approaching T=0 for fields Bab and c and show that their ratio slightly exceeds the mean mass anisotropy of 4.4 derived from our full-relativistic local-density-approximation band structure calculations, also in accord with recent preliminary penetration depth data by Eskildsen et al. [Eskildsen, Forgan, and Kawano-Furukawa, Rep. Prog. Phys. 74, 124504 (2011)] near 4. Its slight reduction when approaching T=0 is not a consequence of Pauli limiting as in less perfect samples but points likely to a multiband effect. We also report irreversibility field data obtained from ac susceptibility measurements. The double-maximum in the T dependence of its imaginary part for fields Bc indicates a peak effect in the T dependence of critical currents.

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  • Received 28 October 2011
  • Corrected 4 May 2012

DOI:https://doi.org/10.1103/PhysRevB.85.134533

©2012 American Physical Society

Corrections

4 May 2012

Erratum

Publisher’s Note: Specific heat and upper critical fields in KFe2As2 single crystals [Phys. Rev. B 85, 134533 (2012)]

M. Abdel-Hafiez, S. Aswartham, S. Wurmehl, V. Grinenko, C. Hess, S.-L. Drechsler, S. Johnston, A. U. B. Wolter, B. Büchner, H. Rosner, and L. Boeri
Phys. Rev. B 85, 179901 (2012)

Authors & Affiliations

M. Abdel-Hafiez*, S. Aswartham, S. Wurmehl, V. Grinenko, C. Hess, S.-L. Drechsler, S. Johnston, A. U. B. Wolter, and B. Büchner

  • Leibniz-Institute for Solid State and Materials Research, (IFW)-Dresden, D-01171 Dresden, Germany

H. Rosner

  • Max-Planck-Institute for Chemistry of Solid Materials (CPfS), D-01187 Dresden, Germany

L. Boeri

  • Max-Planck-Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany

  • *m.mohamed@ifw-dresden.de

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Issue

Vol. 85, Iss. 13 — 1 April 2012

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