The Eliashberg study of the electron–phonon superconductivity in YSn3YSn3 compound

• The superconducting state in YSn3.
• The value of the critical temperature.
• The non BCS value of the thermodynamic parameters.

The superconductivity in YSn3YSn3 is induced by the electron–phonon interaction. The most relevant thermodynamic parameters of the superconducting state for the considered compound have been determined in the framework of the Eliashberg formalism. On the basis of the numerical calculations, it has been shown that the critical temperature (TC)(TC) is equal to 6.52 K. The obtained result accurately reproduces the experimental value of TCTC, which is equal to ∼7 K. Next, the low-temperature value of the order parameter (Δ(0)Δ(0)) has been determined, as well as the thermodynamic critical field (HC(0))(HC(0)), and the specific heat jump at the critical temperature (ΔC(TC))(ΔC(TC)). It has been found that the dimensionless ratios: RΔ≡2Δ(0)/kBTC,RH≡TCCN(TC)/HC2(0), and RC≡ΔC(TC)/CN(TC)RC≡ΔC(TC)/CN(TC), where CNCN denotes the specific heat for the normal state, take the values fairly exceeding the predictions of the BCS theory. In particular, it has been obtained: 3.97, 0.149 and 2.19, respectively. Let us note that the theoretical result for RCRC is in agreement with the existing experimental data.