Anomalous metallic state in quasi-two-dimensional BaNiS$_{2}$

TL;DR

This study reveals unconventional metallic behavior in high-quality BaNiS$_2$ crystals, characterized by large hole mobility, a Dirac-like band, and anomalies suggesting departure from Fermi-liquid theory, linked to AF fluctuations and Hund coupling.

Contribution

The paper provides the first comprehensive analysis of BaNiS$_2$'s thermodynamic and electronic properties, highlighting its anomalous metallic state and potential non-Fermi-liquid behavior.

Findings

Large hole mobility (~15000 cm$^2$V$^{-1}$s$^{-1}$) below 100 K

Presence of a Dirac-like band structure

Crossover from Bloch-Grüneisen to linear resistivity at 2 K

Abstract

We report on a systematic study of the thermodynamic, electronic and charge transport properties of high-quality single crystals of BaNiS$_2$, the metallic end-member of the quasi-twodimensional BaCo$_{1-x}$Ni$_x$S$_2$ system characterized by a metal-insulator transition at $x_{cr}=0.22$. Our analysis of magnetoresistivity and specific heat data consistently suggests a picture of compensated semimetal with two hole- and one electron-bands, where electron-phonon scattering dominates charge transport and the minority holes exhibit, below $\sim$100 K, a very large mobility, $\mu_h\sim$ 15000 cm$^2$V$^{-1}$s$^{-1}$, which is explained by a Dirac-like band. Evidence of unconventional metallic properties is given by an intriguing crossover of the resistivity from a Bloch-Gr\"uneisen regime to a linear$-T$ regime occurring at 2 K and by a strong linear term in the paramagnetic susceptibility above 100 K. We discuss the possibility that these anomalies reflect a departure from conventional Fermi-liquid properties in presence of short-range AF fluctuations and of a large Hund coupling.