title: Heavy fermions. Unconventional Fermi surface in an insulating state.
abstract: Insulators occur in more than one guise; a recent finding was a class of topological insulators, which host a conducting surface juxtaposed with an insulating bulk. Here, we report the observation of an unusual insulating state with an electrically insulating bulk that simultaneously yields bulk quantum oscillations with characteristics of an unconventional Fermi liquid. We present quantum oscillation measurements of magnetic torque in high-purity single crystals of the Kondo insulator SmB6, which reveal quantum oscillation frequencies characteristic of a large three-dimensional conduction electron Fermi surface similar to the metallic rare earth hexaborides such as PrB6 and LaB6. The quantum oscillation amplitude strongly increases at low temperatures, appearing strikingly at variance with conventional metallic behavior.
authors.affiliation: Cavendish Laboratory, Cambridge University, JJ Thomson Avenue, Cambridge CB3 OHE, UK.
authors.forename: B S
authors.initials: BS
authors.lastname: Tan
authors.affiliation: Cavendish Laboratory, Cambridge University, JJ Thomson Avenue, Cambridge CB3 OHE, UK.
authors.forename: Y-T
authors.initials: YT
authors.lastname: Hsu
authors.affiliation: National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA.
authors.forename: B
authors.initials: B
authors.lastname: Zeng
authors.affiliation: Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
authors.forename: M Ciomaga
authors.initials: MC
authors.lastname: Hatnean
authors.affiliation: National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, NM 87504, USA.
authors.forename: N
authors.initials: N
authors.lastname: Harrison
authors.affiliation: National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, NM 87504, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Zhu
authors.affiliation: Cavendish Laboratory, Cambridge University, JJ Thomson Avenue, Cambridge CB3 OHE, UK.
authors.forename: M
authors.initials: M
authors.lastname: Hartstein
authors.affiliation: Cavendish Laboratory, Cambridge University, JJ Thomson Avenue, Cambridge CB3 OHE, UK.
authors.forename: M
authors.initials: M
authors.lastname: Kiourlappou
authors.affiliation: Cavendish Laboratory, Cambridge University, JJ Thomson Avenue, Cambridge CB3 OHE, UK.
authors.forename: A
authors.initials: A
authors.lastname: Srivastava
authors.affiliation: Center for Computational Materials Science, Naval Research Laboratory, Washington, DC 20375, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Johannes
authors.affiliation: National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA.
authors.forename: T P
authors.initials: TP
authors.lastname: Murphy
authors.affiliation: National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA.
authors.forename: J-H
authors.initials: JH
authors.lastname: Park
authors.affiliation: National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA.
authors.forename: L
authors.initials: L
authors.lastname: Balicas
authors.affiliation: Cavendish Laboratory, Cambridge University, JJ Thomson Avenue, Cambridge CB3 OHE, UK.
authors.forename: G G
authors.initials: GG
authors.lastname: Lonzarich
authors.affiliation: Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
authors.forename: G
authors.initials: G
authors.lastname: Balakrishnan
authors.affiliation: Cavendish Laboratory, Cambridge University, JJ Thomson Avenue, Cambridge CB3 OHE, UK. suchitra@phy.cam.ac.uk.
authors.forename: Suchitra E
authors.initials: SE
authors.lastname: Sebastian