title: Closing the spin gap in the Kondo insulator Ce3Bi4Pt3 at high magnetic fields
abstract: Kondo insulator materials--such as CeRhAs, CeRhSb, YbB12, Ce3Bi4Pt3 and SmB6--are 3d, 4f and 5f intermetallic compounds that have attracted considerable interest in recent years. At high temperatures, they behave like metals. But as temperature is reduced, an energy gap opens in the conduction band at the Fermi energy and the materials become insulating. This contrasts with other f-electron compounds, which are metallic at all temperatures. The formation of the gap in Kondo insulators has been proposed to be a consequence of hybridization between the conduction band and the f-electron levels, giving a 'spin' gap. If this is indeed the case, metallic behaviour should be recovered when the gap is closed by changing external parameters, such as magnetic field or pressure. Some experimental evidence suggests that the gap can be closed in SmB6 (refs 5, 8) and YbB12 (ref. 9). Here we present specific-heat measurements of Ce3Bi4Pt3 in d.c. and pulsed magnetic fields up to 60 tesla. Numerical results and the analysis of our data using the Coqblin-Schrieffer model demonstrate unambiguously a field-induced insulator-to-metal transition.
authors.affiliation: Los Alamos National Laboratory, New Mexico 87545, USA. mjaime@lanl.gov
authors.initials: M
authors.lastname: Jaime
authors.initials: R
authors.lastname: Movshovich
authors.initials: GR
authors.lastname: Stewart
authors.initials: WP
authors.lastname: Beyermann
authors.initials: MG
authors.lastname: Berisso
authors.initials: MF
authors.lastname: Hundley
authors.initials: PC
authors.lastname: Canfield
authors.initials: JL
authors.lastname: Sarrao