Evidence of Strong Correlations and Coherence-Incoherence Crossover in the Iron Pnictide Superconductor KFe2As2

F. Hardy; A. E. Boehmer; D. Aoki; P. Burger; T. Wolf; P. Schweiss; R. Heid; P. Adelmann; Y. X. Yao; G. Kotliar; J. Schmalian; C. Meingast

doi:10.1103/physrevlett.111.027002

arXiv · 1302.1696

Evidence of Strong Correlations and Coherence-Incoherence Crossover in the Iron Pnictide Superconductor KFe2As2

F. Hardy·A. E. Boehmer·D. Aoki·P. Burger·T. Wolf·P. Schweiss·R. Heid·P. Adelmann·Y. X. Yao·G. Kotliar·J. Schmalian·C. Meingast

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Abstract

Using resistivity, heat-capacity, thermal-expansion, and susceptibility measurements we study the normal-state behavior of KFe2As2. We find that both the Sommerfeld coefficient gamma = 103 mJ mol-1 K-2 and the Pauli susceptibility chi = 4x10-4 are strongly enhanced, which confirm the existence of heavy quasiparticles inferred from previous de Haas-van Alphen and ARPES experiments. We discuss this large enhancement using a Gutzwiller slave-boson mean-field calculation, which reveals the proximity of KFe2As2 to an orbital-selective Mott transition. The temperature dependence of the magnetic susceptibility and the thermal expansion provide strong experimental evidence for the existence of a coherence-incoherence crossover, similar to what is found in heavy fermion and ruthenate compounds, due to Hund's coupling between orbitals.

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F. Hardy, A. E. Boehmer, D. Aoki, P. Burger, T. Wolf, P. Schweiss, R. Heid, P. Adelmann, Y. X. Yao, G. Kotliar, J. Schmalian, C. Meingast. 2013-02-07. Evidence of Strong Correlations and Coherence-Incoherence Crossover in the Iron Pnictide Superconductor KFe2As2. https://doi.org/10.1103/physrevlett.111.027002

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