Unusual high-field metal in a Kondo insulator

Abstract

Within condensed-matter systems, strong electronic interactions often lead to exotic quantum phases. A recent manifestation of this is the unexpected observation of magnetic quantum oscillations and metallic thermal transport, both properties of systems with Fermi surfaces of itinerant quasiparticles, in the Kondo insulators SmB6 and YbB${}_{12}$. To understand these phenomena, it is informative to study their evolution as the energy gap of the Kondo-Insulator state is closed by a large magnetic field. We show here that both the quantum-oscillation frequency and the cyclotron mass display a strong field dependence in the resulting high-field metallic state in ${}_{12}$. By tracking the Fermi-surface area, we conclude that the same quasiparticle band gives rise to the quantum oscillations in both insulating and metallic states. These data are understood most simply using a two-fluid picture where unusual quasiparticles, contributing little or nothing to charge transport, coexist with conventional fermions. In the metallic state this leads to a heavy-fermion bad metal with negligible magnetoresistance, relatively high resistivity and a very large Kadowaki-Woods ratio, underlining the exotic nature of the fermion ensemble inhabiting ${}_{12}$.

11 pages, 3 figures. This is the original submitted version. Final version is accepted for publication in Nature Physics

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• Topological surface conduction in Kondo insulator YbB${}_{12}$
• Quantum Oscillations in the Magnetisation and Density of States of Insulators
• Hall anomaly, Quantum Oscillations and Possible Lifshitz Transitions in Kondo Insulator YbB${}_{12}$: Evidence for Unconventional Charge Transport
• Evidence of electronic phase separation in the strongly correlated semiconductor YbB12
• Charge neutral fermions and magnetic field driven instability in insulating YbIr${}_3$Si${}_7$
• Magnetoquantum Oscillations in the Specific Heat of a Topological Kondo Insulator
• Quasi-2D anomalous Hall Mott insulator of topologically engineered Jeff =1/2 electrons
• Breakdown of bulk-projected isotropy in surface electronic states of topological Kondo insulator SmB${}_6$(001)
• Rashba-splitting-induced topological flat band detected by anomalous resistance oscillations beyond the quantum limit in ZrTe${}_5$
• Emergence of electronic modes by doping Kondo insulators in the Kondo lattice and periodic Anderson models
• Gapped Spin Excitation in Magnetic Ordered State on Yb-Based Zigzag Chain Compound YbAgSe2
• Temperature-driven change in band structure reflecting spin-charge separation of Mott and Kondo insulators
• Topological surface states in the Kondo insulator YbB${}_{12}$ revealed via planar tunneling spectroscopy
• Quantum oscillations in the heat capacity of Kondo insulator YbB12
• Search for magnetoacoustic quantum oscillations in the insulating phase of YbB${}_{12}$
• Fermi surface and Berry phase analysis for Dirac nodal line semimetals: cautionary tale to SrGa${}_2$ and BaGa${}_2$
• Anomalous 4$f$ fine structure in TmSe${}_{1-x}$Te${}_x$ across the metal-insulator transition