Single-Gap Superconductivity of K0.8Fe1.7(Se0.72S0.28)2 Determined Using Tunneling and Andreev Spectroscopy

Abstract

For the first time, using tunneling and Andreev spectroscopies of planar break-junctions, we have studied the properties of the superconducting subsystem of K_0.8Fe_1.7(Se_0.72S_0.28)₂ iron selenide single crystals with a natural phase separation. We have directly determined its energy characteristics: the magnitude of the superconducting order parameter Δ(0), and its characteristic ratio 2Δ(0)/k_BT_c. The obtained temperature behavior of the critical current I_c(T)/I_c(0) could be fitted with Ambegaokar-Baratoff formula using the experimental 2Δ(0)/k_BT_c value.