The electronic structure of {\em R}NiC$_2$ intermetallic compounds

TL;DR

This study uses first-principles calculations to analyze the electronic structures and Fermi surface nesting of RNiC2 compounds, linking these features to charge-density wave phenomena and magnetic properties.

Contribution

It provides the first detailed electronic structure and susceptibility analysis of RNiC2 compounds, connecting Fermi surface nesting to charge-density wave behavior.

Findings

Strong susceptibility peaks in SmNiC2, GdNiC2, NdNiC2 linked to charge-density waves

Absence of peaks in LaNiC2 correlates with lack of CDW transition

Ferromagnetic SmNiC2 shows suppressed CDW due to magnetic order

Abstract

First-principles calculations of the electronic structure of members of the $R$NiC$_2$ series are presented, and their Fermi surfaces investigated for nesting propensities which might be linked to the charge-density waves exhibited by certain members of the series ($R$ = Sm, Gd and Nd). Calculations of the generalized susceptibility, $\chi_{0}({\bf q},\omega)$, show strong peaks at the same ${\bf q}$-vector in both the real and imaginary parts for these compounds. Moreover, this peak occurs at a wavevector which is very close to that experimentally observed in SmNiC$_2$. In contrast, for LaNiC$_2$ (which is a superconductor below 2.7K) as well as for ferromagnetic SmNiC$_2$, there is no such sharp peak. This could explain the absence of a charge-density wave transition in the former, and the destruction of the charge-density wave that has been observed to accompany the onset of ferromagnetic order in the latter.