Dresden 2009 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 40: Superconductivity: Ferropnictides 1

TT 40.5: Talk

Thursday, March 26, 2009, 15:00–15:15, HSZ 03

Strong coupling of superconductivity to c/a in Ba(Fe,Co)₂As₂ — •Christoph Meingast¹, Frederic Hardy¹, Peter Adelmann¹, Peter Schweiss¹, Doris Ernst¹, Hilbert v. Löhneysen^1,2, and Thomas Wolf¹ — ¹Forschungszentrum Karlsruhe, Institut für Festkörperphysik, — ²Physikalisches Institut, Universität Karlsruhe, D-76128 Karlsruhe, Germany.

Just as in the cuprates, magnetism and superconductivity occur in close proximity to each other in the newly discovered FeAs-based materials. Here, using high-resolution thermal expansion and specific heat measurements, we study the thermodynamic response of the lattice parameters to superconducting and magnetic order in Ba(Fe,Co)₂As₂ single crystals. We show that there is a strong coupling of the c/a ratio to both the superconducting and magnetic/structural phase transitions. According to the Ehrenfest relationship, the ordering temperatures of both ordered states are expected to increase with increasing c/a. This suggests that the occurrence of superconductivity is strongly linked to the magnetic/structural transition.