Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 21: Superconductivity: Poster Session

TT 21.15: Poster

Monday, March 16, 2015, 15:00–18:00, Poster B

Electronic correlations in the superconductors AFe₂As₂ with A = K, Rb, and Cs — •Kai Grube¹, Felix Eilers¹, Diego A. Zocco¹, Peter Schweiss¹, Rolf Heid¹, Thomas Wolf¹, and Hilbert von Löhneysen^1,2 — ¹Karlsruhe Institute of Technology, Institut für Festkörperphysik, 76021 Karlsruhe, Germany — ²Karlsruhe Institute of Technology, Physikalisches Institut, 76131 Karlsruhe, Germany

Superconductivity in iron pnictides and chalcogenides occurs in the proximity to antiferromagnetic order, giving rise to the assumption that the superconductivity is unconventional and originates from electron-electron interactions. So far, experimental and theoretical studies underpin this assumption but fail to unravel the pairing mechanism. A central question is the role of electronic correlations in these materials. We have investigated the thermal expansion and magnetostriction of the stoichiometric compounds AFe₂As₂ with A = K, Rb, and Cs. Our measurements show a huge increase of the effective mass quasiparticles m_eff with increasing A ion radius, while the superconducting transition temperature T_c decreases. The relation between superconductivity and electronic correlations will be discussed by using the uniaxial pressure dependences of T_c and m_eff and the temperature dependence of the upper critical field.