Direct observation of the influence of the FeAs₄ tetrahedron on superconductivity and antiferromagnetic correlations in Sr₂VO₃FeAs

¹ European Synchrotron Radiation Facility (ESRF) - BP 220, 6 Rue Jules Horowitz, F-38043 Grenoble, France, EU
² Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica (CNEA) Avda. General Paz y Constituyentes, 1650, San Martín, Argentina
³ Instituto Sabato, Universidad Nacional de San Martín, CNEA - 1650, San Martín, Argentina
⁴ Institut Néel, Centre National de la Recherche Scientifique (CNRS) and Université Joseph Fourier (UJF) BP 166, 25 Avenue des Martyrs, F-38042 Grenoble Cedex 9, France, EU
⁵ CRETA (CNRS) - BP 166, 25 Avenue des Martyrs, F-38042 Grenoble Cedex 9, France, EU
⁶ National Laboratory for Superconductivity, Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences - P.O. Box 603, Beijing 100190, China

^a nunez@grenoble.cnrs.fr

Received: 20 July 2011
Accepted: 7 October 2011

Abstract

We measure the pressure dependence of the electrical resistivity and the crystal structure of iron superconductor Sr₂VO₃FeAs. Below ∼10 GPa the structure compresses but remains undeformed, with regular FeAs₄ tetrahedrons, and a constant T_c. Beyond 10 GPa, the tetrahedron strongly distorts, while T_c goes gradually to zero. Band structure calculations of the undistorted structure show multiple-nesting features that hinder the development of an antiferromagnetic (AF) ground state, allowing the appearance of superconductivity. The deformation of the tetrahedra that breaks band degeneracy degrades multiple nesting, thus favouring one particular AF state at the expense of T_c.