Suppression of the energy gap in SmB6 under pressure

The electrical resistance R of SmB6 as a function of temperature T and pressure P has been measured in the range 1 K<∼T<∼300 K and 0< 220 kbar. The behavior of R(T) changes continuously from that of a narrow gap semiconductor to that of a metal in the range of 0< 70 kbar. The dependence of R on T and P can be analyzed phenomenologically within the context of a thermal activation model with an activation energy that decreases linearly with pressure from 33 K at zero pressure to zero at 70 kbar. The data resemble those of SmS and SmSe under pressure and suggest a general behavior of R(T,P) for intermediate-valence Sm compounds.