Pressure-induced Kondo semiconductor: The filled skutterudite compoundCeRu4Sb12

Abstract

We report electrical transport and x-ray studies under high pressure of the filled skutterudite compound ${\text{CeRu}}_{4}{\text{Sb}}_{12}$. Electrical resistivity measurements in the temperature range 2--300 K and under hydrostatic pressures up to 10.0 GPa have revealed a pressure-induced metal-semiconductor transition above 5.0 GPa in ${\text{CeRu}}_{4}{\text{Sb}}_{12}$. The energy gap in the semiconducting state of ${\text{CeRu}}_{4}{\text{Sb}}_{12}$ estimated from an activation law increases with a pressure coefficient of $\ensuremath{\sim}12\text{ }\text{K}/\text{GPa}$. On the other hand, a high-pressure x-ray study has determined the relationship between lattice constant and energy gap of ${\text{CeRu}}_{4}{\text{Sb}}_{12}$ under high pressure. We suggest that an electronic mechanism of a semiconducting state in ${\text{CeRu}}_{4}{\text{Sb}}_{12}$ under high pressure could originate from an enhanced $c\ensuremath{-}f$ hybridization and that the $P$-induced state could be categorized as a Kondo semiconductor.