An observation of electron phase transition in SmB6 at low temperatures

In order to reveal the nature of the ground state of archetypal intermediate-valence compound SmB6, a comprehensive study of its transport and magnetic properties was carried out on high-quality single crystals at temperatures of 1.8–300 K in magnetic fields up to 7 T. A drastic enhancement of negative magnetoresistance was observed below 14 K, with the maximum absolute value of Δρ/ρB2∼2.2×10−3 T−2 at T≈5.2 K. This effect seems to be attributable to anomalous magnetic scattering of many-body (exciton–polaronic) complexes induced by fast valence fluctuations on Sm sites. The observed anomalies of magnetotransport, thermoelectric and magnetic characteristics are discussed in terms of electron phase transition to the coherent state of interacting many-body complexes occurring at T*∼5 K.