Novel Quantum Criticality in CeRu$_2$Si$_2$ near Absolute Zero Observed by Thermal Expansion and Magnetostriction

TL;DR

This study investigates quantum criticality in CeRu$_2$Si$_2$ at ultra-low temperatures using thermal expansion and magnetostriction, revealing non-Fermi-liquid behavior indicative of a nearby quantum critical point.

Contribution

First to observe non-Fermi-liquid effects and suggest an additional quantum critical point in CeRu$_2$Si$_2$ at millikelvin temperatures using thermal expansion and magnetostriction measurements.

Findings

Fermi-liquid behavior above 50 mK

Non-Fermi-liquid effects below 50 mK

Evidence for an additional quantum critical point

Abstract

We report linear thermal expansion and magnetostriction measurements for CeRu$_2$Si$_2$ in magnetic fields up to 52.6 mT and at temperatures down to 1 mK. At high temperatures, this compound showed Landau-Fermi-liquid behavior: The linear thermal expansion coefficient and the magnetostriction coefficient were proportional to the temperature and magnetic field, respectively. In contrast, a pronounced non-Fermi-liquid effect was found below 50 mK. The negative contribution of thermal expansion and magnetostriction suggests the existence of an additional quantum critical point.