Electronic structure, lattice dynamics, and magnetic properties of ThXAsN (X=Fe, Co, Ni) superconductors: A first-principles study
Journal
Physical Review B
Journal Volume
102
Journal Issue
22
Date Issued
2020
Author(s)
Sen S., Guo G.-Y.
Abstract
In this work, we present a comparative first-principles study of the mechanical properties, electronic structure, phonon dispersion relation, electron-phonon coupling, and magnetism in three isostructural superconductors, namely ThFeAsN, ThCoAsN, and ThNiAsN. Experimentally, ThFeAsN and ThNiAsN show superconducting properties, while ThCoAsN has not been synthesized. Our calculated elastic constants show that all these systems are mechanically stable. Significant differences in the electronic structures of these three compounds in terms of density of states, band structures, and Fermi surfaces are found. Our phonon calculations reveal that all the systems, including ThCoAsN, are dynamically stable. Phonon dispersion relations indicate that the optical modes of all three systems are almost the same, while there are significant variations in the low-frequency manifold consisting of mixed modes. The electron-phonon coupling constants and superconducting transition temperatures calculated based on the Eliashberg formalism predict a rather high Tc of 6.4 K for ThCoAsN and also a Tc of 3.4 K for ThNiAsN, which agrees well with the experimental value of 4.3 K. Nevertheless, we find a Tc of 0.05 K for ThFeAsN, which is much smaller than the experimental Tc of ~30 K. However, a simple analysis considering the amplifying effects of spin density wave order and out-of-plane soft phonon modes suggests that the Tc could be increased considerably to ~10 K. Finally, we also discuss the effect of anion As height on the electronic structures, and we study possible magnetic states in these three compounds. ? 2020 American Physical Society.
Subjects
Acoustic dispersion; Arsenic compounds; Calculations; Cobalt compounds; Crystal lattices; Density (optical); Electron correlations; Electron-phonon interactions; Electronic structure; Iron compounds; Iron-based Superconductors; Magnetism; Nickel compounds; Quantum theory; Spin density waves; Strain measurement; Superconducting transition temperature; Technetium; Thorium compounds; Electron phonon couplings; Electron-phonon coupling constant; Experimental values; First-principles study; Mechanically stable; Phonon dispersion relations; Spin-density-wave order; Superconducting properties; Nitrogen compounds
SDGs
Type
journal article