Pristine quantum criticality in a Kondo semimetal

TL;DR

This paper reports the discovery of intrinsic quantum criticality in the Kondo semimetal CeRu$_4$Sn$_6$, characterized by scale-invariant behavior across the Brillouin zone, suggesting a new class of quantum critical phenomena in semimetals.

Contribution

It provides experimental evidence of quantum criticality in a Kondo semimetal without external tuning, highlighting potential universality of Kondo destruction in semimetallic systems.

Findings

Power-law divergence of magnetic Gr"unesien ratio

Energy over temperature scaling in neutron response

Temperature as the sole energy scale in criticality

Abstract

The observation of quantum criticality in diverse classes of strongly correlated electron systems has been instrumental in establishing ordering principles, discovering new phases, and identifying the relevant degrees of freedom and interactions. At focus so far have been insulators and metals. Semimetals, which are of great current interest as candidate phases with nontrivial topology, are much less explored in experiments. Here we study the Kondo semimetal CeRu$_4$Sn$_6$ by magnetic susceptibility, specific heat, and inelastic neutron scattering experiments. The power-law divergence of the magnetic Gr\"unesien ratio reveals that, surprisingly, this compound is quantum critical without tuning. The dynamical energy over temperature scaling in the neutron response, seen throughout the Brillouin zone, as well as the temperature dependence of the static uniform susceptibility indicate that temperature is the only energy scale in the criticality. Such behavior, which has been associated with Kondo destruction quantum criticality in metallic systems, may well be generic in the semimetal setting.