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TT: Fachverband Tiefe Temperaturen

TT 53: Superconductivity: Fe-based Superconductors - 122

TT 53.1: Vortrag

Mittwoch, 2. April 2014, 09:30–09:45, HSZ 201

The Pauli-limited multiband superconductor RbFe₂As₂ — •Felix Eilers, Diego A. Zocco, Thomas Wolf, Peter Schweiss, Kai Grube, and Hilbert v. Löhneysen — Karlsruher Institut für Technologie, Institut für Festkörperphysik, Karlsruhe, Germany

The compounds AFe₂As₂ - where A denotes an alkali metal element like K or Rb - offer the possibility to probe the unconventional superconductivity in iron pnictides. The upper critical magnetic fields H_c2 are easily accessible and no additional chemical disorder is introduced by substitutional atoms. We measured the thermal expansion and magnetostriction of a RbFe₂As₂ single crystal at temperatures T between 50 mK and 4 K and magnetic fields µ₀H up to 14 T. The quantum oscillations observed in our magnetostriction measurements indicate a strongly correlated electron system in accordance with the enhanced Sommerfeld coefficient and Pauli susceptibility of KFe₂As₂ [1]. In addition, they reveal, together with the thermal expansion, the multiband character of the electronic structure and superconductivity. The T-H phase diagram constructed from our field-dependent measurements shows the typical behavior of an orbitally limited superconductor for H parallel to the c-axis, while for H within the ab-plane the superconducting phase transition becomes discontinuous below T = 1.2 K. For this field direction the orbital limit strongly exceeds H_c2(T = 0), thus pointing to a Pauli-limited upper critical field like in KFe₂As₂ [2].
F. Hardy et al., PRL 111, 027002 (2013)
D. A. Zocco et al., PRL 111, 057007 (2013)