Electronic and lattice properties of non-centrosymmetric superconductors ThTSi (T = Co, Ir, Ni, and Pt)

TL;DR

This study investigates the electronic, lattice, and superconducting properties of ThTSi compounds (T = Co, Ni, Ir, Pt), highlighting spin-orbit effects, phonon behaviors, and potential pairing mechanisms using density functional theory.

Contribution

It provides a comprehensive theoretical analysis of electronic structures, phonon dispersions, and superconducting pairing possibilities in non-centrosymmetric ThTSi compounds.

Findings

Spin-orbit coupling causes band splitting, more pronounced with heavier T atoms.

Low-energy phonon modes indicate potential dynamic instability in some compounds.

Phonon contributions to heat capacity are quantitatively analyzed.

Abstract

The theoretical studies on the electronic and lattice properties of the series of non-centrosymmetric superconductors ThTSi, where T = Co, Ni, Ir, and Pt are presented. The electronic band structure and crystal parameters were optimized within the density functional theory. The spin-orbit coupling leads to the splitting of the electronic bands and Fermi surfaces, with the stronger effect observed for the compounds with the heavier atoms Ir and Pt. The possible mixing of the spin-singlet and spin-triplet pairing in the superconducting state is discussed. The phonon dispersion relations and phonon density of states were obtained using the direct method. The dispersion curves in ThCoSi and ThIrSi exhibit the low-energy modes along the S-N-S0 line with the tendency for softening and dynamic instability. Additionally, we calculate and analyse the contributions of phonon modes to lattice heat capacity.