The chemical states and electronic states of layered carbide superconductor ThMo₂Si₂C

Abstract

Understanding the chemical states and electronic states of superconducting materials can help researchers to grasp their superconducting mechanisms. Then, through doping, high pressure or other methods, the Tc (Critical Temperature) can be boosted. Recently, a new layered carbide superconductor ThMo2Si2C was discovered. Its chemical states and electronic states are unknown. Here, the chemical states of ThMo2Si2C are investigated using X-ray photoelectron spectroscopy assisted with argon ion sputtering and Raman spectroscopy. The physical significance behind them is elucidated. Its electronic states are investigated by first-principles calculations. It is found that the major contribution to the total DOS (Density of States) is from Mo 4d state, which plays the dominant role in the superconductivity of ThMo2Si2C. The hybridization between Th 6d and Mo 4d is very weak. Thus, a separation of the structure into independent Mo-C-Si and Th subunits (layers) is justified from the point of view of electronic structure. A flat band along the A-M high-symmetry direction is observed near the Fermi level. The influence of the interlayer distance between Mo-C-Si units (layers) on the DOS and band structure is investigated by first-principles calculations too.

ThCr2Si2C: An Antiferromagnetic Metal with a Cr2C Square Lattice

“…Recently, we reported a new superconductor, ThMo 2 Si 2 C, with a critical temperature of 2.2 K. The conducting Mo 2 Si 2 C layer in ThMo 2 Si 2 C exhibits an isostructural relationship with the Ti 2 Pn 2 O layers found in previously discovered BaTi 2 Pn 2 O ( Pn = Sb, Bi) superconductors. , First-principles calculations have demonstrated that the density of states near the Fermi surface in ThMo 2 Si 2 C is primarily contributed by the Mo 4d orbital . Notably, ThMo 2 Si 2 C is the only superconducting member among the R Mo 2 Si 2 C family ( R represents rare earth elements), while others containing lanthanide elements ( Ln Mo 2 Si 2 C) behave as nonsuperconducting metals and exhibit Pauli paramagnetism. , This observation suggests that the superconductivity in ThMo 2 Si 2 C may be associated with the band-filling effects on the Mo 4d orbital resulting from the substitution of Th 4+ for Ln 3+ .…”

“…10,11 First-principles calculations have demonstrated that the density of states near the Fermi surface in ThMo 2 Si 2 C is primarily contributed by the Mo 4d orbital. 12 Notably, ThMo 2 Si 2 C is the only superconducting member among the RMo 2 Si 2 C family (R represents rare earth elements), while others containing lanthanide elements (LnMo 2 Si 2 C) behave as nonsuperconducting metals and exhibit Pauli paramagnetism. 13,14 This observation suggests that the superconductivity in ThMo 2 Si 2 C may be associated with the band-filling effects on the Mo 4d orbital resulting from the substitution of Th 4+ for Ln 3+ .…”