Superconductivity and vortex pinning in Fe_1.04Te_0.60Se_0.40 single crystal

Max-Planck-Institut für Festkörperforschung - Heisenbergstraße 1, D-70569 Stuttgart, Germany, EU

Received: 30 August 2010
Accepted: 12 November 2010

Abstract

Measurements of specific heat, resistivity, and magnetic hysteresis loop were performed on high-quality Fe_1.04Te_0.60Se_0.40 single crystal. The exponential decay of the specific heat of the sample can be well described by the BCS-weak coupling theory. The resistive upper critical fields H_c2 were extracted with the zero-resistance criteria. The slopes dH_c2^ab /dT and dH_c2^c /dT collected from the existing data in the iron chalcogenide family are roughly scaled by the relation dH_c2 /dT∝T_c for both H||c and H||ab configurations, which can be interpreted in terms of a pair-breaking effect. Comparing the AFe₂As₂ superconductors, the second magnetization peak observed in the magnetic hysteresis loops for H||c is strongly broadened for the Fe_1.04Te_0.60Se_0.40 single crystal. We demonstrate that the δT_c pinning associated with spatial fluctuations of the transition temperatures gives rise to the broadening of the second peak.