Study of anisotropy in the superconducting properties of FeTe0.55Se0.45 single crystal grown by the self-flux method

Abstract

We report anisotropy in the superconducting properties of FeTe0.55Se0.45 bulk single crystal synthesized via the self-flux method. We have performed magnetotransport, magnetic and heat capacity measurements on single crystals of same batch. The grown crystals have also been characterized by XRD, XPS and Raman measurements. The superconductivity at T C ∼ 14 K has been affirmed by the temperature-dependent resistivity, magnetic, and specific heat measurements. The anisotropy in the upper critical field (H C2), coherence length (ξ), and critical current density (J C) have been studied from the magnetotransport and magnetic measurements, respectively, under applied magnetic fields of 0–12 T along the ab-plane and c-axis. The critical current density has been estimated by Bean’s critical state model at different magnetic fields (J C(H)) and temperatures (J C(T)) measured for H‖ab-plane and H‖c axis. The anisotropic behaviour has also been observed for J C(H). The presence of ‘peak effect’ or fishtail characteristic has been noticed in M–H loops for H‖c only, which shows a shift towards the lower fields with increasing temperature. The nature of the pinning mechanisms in the sample has been determined by the normalized pinning force density using the Dew Hughes scaling rule, and the analysis of experimental data indicates the presence of δl-pinning in the sample. The temperature-dependent electronic specific heat has been fitted with the exponential law and the evaluated coupling constant 2Δ0/kBTc is ∼3.42 which is close to the universal BCS value of 3.53. The observed low value of residual Sommerfeld coefficient ≈ 4.59 mJ mol−1 K2 indicates good quality of the grown single crystal.