Ab Initio Investigation of the Tin Kagome Sublattice and Phonon-Mediated Superconductivity in SrSn3

Recent studies have shown that the intermetallic compound SrSn3 crystallizes in a layered structure in which Sn atoms form a Kagome framework. As a type-II superconductor with an experimental critical temperature of about 5.5 K, SrSn3 provides an opportunity to examine how the main-group Sn sublattice participates in conventional phonon-mediated superconductivity. Using density-functional theory, linear-response calculations, and electron–phonon coupling analysis, we investigate its structural, electronic, elastic, vibrational, and superconducting properties. The electronic states around the Fermi level are dominated by Sn-p orbitals, whereas mode-resolved electron–phonon calculations show that the most strongly coupled low-frequency modes are predominantly associated with Sn vibrations. Thus, our calculations establish the central role of the Sn sublattice in both the low-energy electronic structure and the dominant electron–phonon interaction. Since this Sn sublattice forms the Kagome framework, the results are consistent with an important role of the Sn Kagome network without attributing the pairing mechanism uniquely to Kagome geometry. A complementary spin–orbit-coupled Wannier analysis is used to examine the low-energy band crossings and the corresponding Berry-curvature response. The calculated average electron–phonon coupling constant is λ = 0.832, yielding Tc = 4.6 K, in reasonable agreement with the experimental value of 5.5 K.