Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session S1: Topological Mysteries in Kondo Insulating SmB6Invited
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Sponsoring Units: DCMP Chair: Lu Li, University of Michigan Room: Ballroom I |
Thursday, March 17, 2016 11:15AM - 11:51AM |
S1.00001: Topologically protected surface states in SmB6 Invited Speaker: Jing Xia |
Thursday, March 17, 2016 11:51AM - 12:27PM |
S1.00002: Two-dimensional Fermi surfaces in Kondo insulating SmB6 Invited Speaker: Gang Li There has been renewed interest in Samarium Hexaboride, which is a strongly correlated heavy Fermion material. Hybridization between itinerant electrons and localized orbitals lead to an opening of charge gap at low temperature. However, the resistivity of SmB$_{6}$ does not diverge at low temperature. Former studies suggested that this residual conductance is contributed by various origins. Recent theoretical developments suggest that the particular symmetry of energy bands of SmB$_{6}$ may host a topologically non-trivial surface state, i.e., a topological Kondo insulator. To probe the Fermiology of the possible metallic surface state, we use sensitive torque magnetometry to detect the de Haas van Alphen (dHvA) effect due to Landau level quantization on flux-grown crystals, down to He-3 temperature and up to 45 Tesla. Our angular and temperature dependent data suggest two-dimensional Fermi Surfaces lie in both crystalline (001) and (101) surface planes of SmB$_{6}$. [Preview Abstract] |
Thursday, March 17, 2016 12:27PM - 1:03PM |
S1.00003: Unconventional bulk three-dimensional Fermi surface in Kondo insulating SmB$_{\mathrm{6}}$ Invited Speaker: Beng Tan We report the observation of a paradoxical insulator with a bulk state which is electrically insulating and simultaneously yields quantum oscillations typical of good metals. We present high field measurements of conductivity and magnetic torque in high purity single crystals of the Kondo insulator SmB$_{\mathrm{6}}$ which reveal an activated behavior characteristics of an insulator with an energy gap at the Fermi energy in the former and quantum oscillation of frequencies characteristics of a large three-dimensional conduction electron Fermi surface similar to the metallic rare earth hexaborides such as PrB$_{\mathrm{6}}$ and LaB$_{\mathrm{6}}$ in the latter. The quantum oscillations observed in the magnetic torque measurements are characteristic of an unconventional Fermi liquid -- the amplitude strongly increases at low temperatures in a stark contrast to the saturating Lifshitz-Kosevich behavior in conventional metallic states. [Preview Abstract] |
Thursday, March 17, 2016 1:03PM - 1:39PM |
S1.00004: Neutron scattering from the Kondo Insulator SmB6 Invited Speaker: Collin Broholm A review of neutron scattering work probing the Kondo insulator SmB6 is presented with special emphasis on assessing the topology of the underlying strongly renormalized band structure. A 14 meV excition dominates the spectrum and is evidence of strong electron correlations [1]. Though the data generally supports the proposal that SmB6 is a topological Kondo insulator, specific heat and high-resolution neutron scattering data show a continuum of states well below the bulk transport gap, which enrich the problem and may connect to the recent surprising de Haas van Alpen results. \begin{enumerate} [1] “Interaction Driven Subgap Spin Exciton in the Kondo Insulator SmB6,” W.?T. Fuhrman, J. Leiner, P. Nikolic, G.?E. Granroth, M.?B. Stone, M.?D. Lumsden, L. DeBeer-Schmitt, P.?A. Alekseev, J.-M. Mignot, S.?M. Koohpayeh, P. Cottingham, W. Adam Phelan, L. Schoop, T.?M. McQueen, and C. Broholm, Phys. Rev. Lett. {\bf 114}, 036401 (2015). \end{enumerate} [Preview Abstract] |
Thursday, March 17, 2016 1:39PM - 2:15PM |
S1.00005: Kondo Breakdown and Quantum Oscillations in SmB$_6$ Invited Speaker: Onur Erten Motivated by the observation of light surface states of SmB$_6$, I will discuss the effects of surface Kondo breakdown in topological Kondo insulators, in particular SmB$_6$. I will present both numerical and analytic results which show that the decoupling of the localized moments at the surface disturbs the compensation between light and heavy electrons and dopes the Dirac cone. Dispersion of these uncompensated surface states are dominated by inter-site hopping, which leads to much lighter quasiparticles in accordance with ARPES experiments [1]. Another tantalizing result about SmB$_6$ comes from the recent quantum oscillation experiments which lead to completely controversial interpretations. I will discuss a general theoretical viewpoint considering both bulk and surface scenarios and our new interpretation in terms of Kondo breakdown in topological surface states [2]. [1] V. Alexandrov, P. Coleman, O. Erten, Phys. Rev. Lett. 114, 177202 (2015) [2] O. Erten, P. Ghaemi, P. Coleman arXiv: 1510.02313 (2015) [Preview Abstract] |
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