Studies of the correlated electron system SmB6

Kebede, A.; Aronson, M. C.; Buford, C.M.; Canfield, Paul C.; Cho, Jin Hyung; Coles, B.R.; Cooley, J. C.; Coulter, J. Y.; Fisk, Z.; Goettee, J.D.; Hults, W. L.; Lacerda, A.; McLendon, T.D; Tiwari, P.; Smith, James L.

doi:10.1016/0921-4526(96)00092-0

Cited by 28 publications

(23 citation statements)

References 9 publications

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“…Deliberate oxidation after polishing 47 modestly decreased 180405-3 but did not eliminate the residual conductivity, leading to the conclusions that the "saturation behavior is a bulk property" but also that "surface metallic conduction plays a partial role." Based on a finding that etching modestly increased the residual resistivity, Kebede et al 48 proposed that it arises from a residual conducting layer ("surface crud"). Significantly however, even after etching away 10%-30% of the samples' weights, the residual conductivity remained and the authors concluded that "the surface crud is not a discrete layer but rather is continuously changing spatially."…”

Section: 11mentioning

confidence: 99%

Low-temperature surface conduction in the Kondo insulator SmB6

et al. 2013

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We study the transport properties of the Kondo insulator SmB 6 with a specialized configuration designed to distinguish bulk-dominated conduction from surface-dominated conduction. We find that as the material is cooled below 4 K, it exhibits a crossover from bulk to surface conduction with a fully insulating bulk. We take the robustness and magnitude of the surface conductivity, as is manifest in the literature of SmB 6 , to be strong evidence for the topological insulator metallic surface states recently predicted for this material.

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Section: 11mentioning

confidence: 99%

Low-temperature surface conduction in the Kondo insulator SmB6

et al. 2013

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“…Correspondingly, the dc resistivity shows an exponential divergence with reducing temperature, as expected for a gapped system, but then surprisingly plateaus at temperatures T < 5K, suggesting an additional conduction mechanism 20,21 . Although first interpreted as stemming from impurity states 22,23 , the low temperature resistivity plateau has recently been proposed to arise from topological surface states residing within the Kondo gap, suggesting SmB 6 to be the first example of a topological Kondo insulator (TKI) [13][14][15][16][17] . Non-trivial topology is supported by recent calculations which propose SmB 6 possesses three Dirac cones located at high symmetry points of the Brillouin zone 14,16,17 .…”

Section: Introductionmentioning

confidence: 99%

Anomalous three-dimensional bulk ac conduction within the Kondo gap of SmB6 single crystals

et al. 2016

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The Kondo insulator SmB6 has long been known to display anomalous transport behavior at low temperatures, T < 5 K. In this temperatures range, a plateau is observed in the dc resistivity, contrary to the exponential divergence expected for a gapped system. Recent theoretical calculations suggest that SmB6 may be the first topological Kondo insulator (TKI) and propose that the residual conductivity is due to topological surface states which reside within the Kondo gap. Since the TKI prediction many experiments have claimed to observe high mobility surface states within a perfectly insulating hybridization gap. Here, we investigate the low energy optical conductivity within the hybridization gap of single crystals of SmB6 via time domain terahertz spectroscopy. Samples grown by both optical floating zone and aluminum flux methods are investigated to probe for differences originating from sample growth techniques. We find that both samples display significant 3D bulk conduction originating within the Kondo gap. Although SmB6 may be a bulk dc insulator, it shows significant bulk ac conduction that is many orders of magnitude larger than any known impurity band conduction. The nature of these in-gap states and their coupling with the low energy spin excitons of SmB6 is discussed. Additionally, the well defined conduction path geometry of our optical experiments allows us to show that any surface states, which lie below our detection threshold if present, must have a sheet resistance of R/ ≥ 1000 Ω.

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“…The slave boson theory of Kondo materials views this mode as an exciton, which is created by the Coulomb interactions among the narrow-band f electrons and protected against decay by the material's bandgap 13,20 . In addition to this evidence of correlations, some Kondo materials exhibit a characteristic insulating temperature dependence of the DC conductivity until the lowest temperatures where the conductivity saturates at a finite value [37][38][39][40][41] . While this may or may not be related to the existence of a metallic surface, the experimental support for SmB 6 being a TI is growing 36,[42][43][44][45][46][47][48][49][50][51][52] .…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional heavy fermions on the strongly correlated boundaries of Kondo topological insulators

Nikolić¹

2014

Phys. Rev. B

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Samarium hexaboride (SmB6), a representative Kondo insulator, has been characterized recently as a likely topological insulator. It is also a material with strong electron correlations, evident by the temperature dependence of its bandgap and the existence of a nearly flat collective mode whose energy lies within the bandgap. Similar strong correlations can affect or even destabilize the two-dimensional metallic state of topological origin at the crystal boundary. Here we construct the minimal lattice model of the correlated boundary of topological Kondo insulators, and make phenomenological predictions for its possible ground states. Depending on the microscopic properties of the interface between the topological Kondo material and a conventional insulator, the boundary metal can exhibit a varied degree of hybridization between the d and f orbitals of the rare earth element, yielding a rich two-dimensional heavy fermion phenomenology. A pronounced participation of the f orbitals is expected to create a heavy fermion Dirac metal, possibly unstable to a spin density wave, electron localization or even superconductivity. The opposite limit of "localized magnetic moments" helped by the partial Kondo screening on the crystal boundary can bring about a non-Fermi liquid of d electrons that exhibits two-dimensional quantum electrodynamics, or other unconventional states. In addition, ultra-thin films made from topological Kondo insulators could open the possibility of creating exotic incompressible quantum liquids with non-Abelian fractional excitations, whose dynamics shaped by the strong Rashba spin-orbit coupling resembles that of fractional quantum Hall systems.

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Studies of the correlated electron system SmB6

Cited by 28 publications

References 9 publications

Low-temperature surface conduction in the Kondo insulator SmB6

Low-temperature surface conduction in the Kondo insulator SmB6

Anomalous three-dimensional bulk ac conduction within the Kondo gap of SmB6 single crystals

Two-dimensional heavy fermions on the strongly correlated boundaries of Kondo topological insulators

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