Multiband superconductivity in KFe2As2: Evidence for one isotropic and several lilliputian energy gaps

Frédéric Hardy, Robert Ederl, Martin Jackson, Dai Aoki, Carley Paulsen, Thomas Wolf, Philipp Burger, Anna Böhmer, Peter Schweiss, Peter Adelmann, Robert A. Fisher, Christoph Meingast

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37 Citations (Scopus)


We report a detailed low-temperature thermodynamic investigation (heat capacity and magnetization) of the superconducting state of KFe 2As2 for H||c axis. Our measurements reveal that the properties of KFe2As2 are dominated by a relatively large nodeless energy gap (δ0 = 1.9 κBTc) which excludes dx2-y2 symmetry. We prove the existence of several additional extremely small gaps (δ0 < 1.0 k BTc) that have a profound impact on the low-temperature and lowfield behavior, similar to MgB2, CeCoIn5, and PrOs4Sb12. The zero-field heat capacity is analyzed in a realistic selfconsistent 4-band BCS model which reproduces only qualitatively the recent laser ARPES results of Okazaki et al. [Science 337, 1314 (2012)]. Our results show that extremely low-temperature measurements, i.e., T < 0.1 K, are required in order to resolve the question of the existence of line nodes in this compound.

Original languageEnglish
Article number014711
Journaljournal of the physical society of japan
Issue number1
Publication statusPublished - 2014 Jan 15

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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