Quantum criticality and disorder in the antiferromagnetic critical point of NiS$_{2}$ pyrite

TL;DR

This study investigates the effects of disorder on quantum criticality in NiS₂ pyrite, revealing that disorder drastically alters resistivity behavior near the antiferromagnetic quantum critical point, with non-Fermi liquid behavior dominating in disordered samples.

Contribution

It demonstrates how disorder influences quantum critical behavior in NiS₂ pyrite, contrasting with cleaner samples, and highlights the suppression of Fermi liquid behavior near the critical point.

Findings

Disorder significantly affects quantum critical resistivity behavior.

Clean NiS₂ pyrite shows different critical behavior than disordered NiS₂-xSeₓ.

Non-Fermi liquid T^{3/2} dependence dominates in disordered samples.

Abstract

A quantum critical point (QCP) between the antiferromagnetic and the paramagnetic phases was realized by applying a hydrostatic pressure of ~ 7 GPa on single crystals of NiS_{2} pyrite with a low residual resistivity, rho_{0}, of 0.5 mu-Omega-cm. We found that the critical behavior of the resistivity, rho, in this clean system contrasts sharply with those observed in its disordered analogue, NiS_{2-x}Se_{x} solid-solution, demonstrating the unexpectedly drastic effect of disorder on the quantum criticality. Over a whole paramagnetic region investigated up to P = 9 GPa, a crossover temperature, defined as the onset of T^{2} dependence of rho, an indication of Fermi liquid, was suppressed to a substantially low temperature T sim 2 K and, instead, a non Fermi liquid behavior of rho, T^{3/2}-dependence, robustly showed up.