Crystal field effects and quadrupole fluctuations in Ce$_3$Au$_3$Sb$_4$ detected by Sb NQR

TL;DR

This study uses Sb NQR to investigate crystal field effects and quadrupole fluctuations in Ce3Au3Sb4, revealing their influence on low-temperature specific heat and nuclear relaxation rates.

Contribution

It provides new insights into quadrupole fluctuations and their impact on physical properties in Ce3Au3Sb4, a narrow gap semiconductor.

Findings

Quadrupole fluctuations influence nuclear relaxation rates.

Crystal electric field effects explain temperature dependence of $ u_Q$.

Quadrupole fluctuations may cause large low-temperature specific heat.

Abstract

We report $^{121,123}$Sb NQR studies on single crystals of the narrow gap semiconductor Ce3Au3Sb4. The temperature dependence of the nuclear quadrupole frequency ($\nu_Q$), as well as the magnetic susceptibility, is well explained by crystal electric field effects. The nuclear spin-lattice relaxation rate ($T_1^{-1}$) of both $^{121}$Sb and $^{123}$Sb increases rapidly with decreasing temperature. The ratio of $T_1^{-1}$ for the two Sb isotopes is constant at high temperature but it decreases at low temperatures, indicating the important role of quadrupole fluctuations of the Ce ions. We propose that quadrupole fluctuations could be the origin of the large specific heat at low temperature via phonon-quadrupole moment coupling.