On the Thermodynamic Properties of FexSe_0.5Te_0.5 Superconducting Single Crystals: An Experimental Study

The variation of the thermodynamic critical fields (Hc) with temperature has been obtained from the equilibrium magnetization of Fe_xSe_0.5Te_0.5 superconducting single-crystal with (0.95 ≤ × ≤ 1.1). Based on the BCS theory, we used the Hc values to obtain the variations in the energy gap Δ(T), the cooper pair coupling, the energy gap ratio 2Δ(0)/k_BT_c, and the specific heat jump Δ C BCS / T c with varying Fe content. We found that the Cooper pairs coupling strength decreases with increasing Fe content within the range (∼3.1 to 2.6) for 1.0 ≤ × ≤ 1.1, which is consistent with the BCS-weak coupling limit for all samples. Moreover, the value of the energy gap is nearly constant at about 3.5 meV for all samples, while the Hc(0)/Tc ratio reaches a maximum near x ∼ 1.05. The obtained values of the energy gap, the coupling strength, and the specific heat ratio are consistent with recently published results using various experimental techniques.