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Topological Kondo Insulators and SmB6: magnetism meets topology.

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The electrons in Heavy fermion materials are subject to spin-orbit coupling nteractions that greatly exceed their Kinetic energy. It has long been known that the spin orbit coupling stablizes new kinds of heavy fermion metals, superconductors and “Kondo insulators” against the competing state of magnetism. I will discuss the latest realization that spin orbit coupling can changing the topology of Kondo insulators, sometimes giving rise to Topological Kondo insulators [2,3] with surface Dirac cones. We’ll specifically discuss SmB6, a KI discovered 45 years ago, predicted to be topological in 2010 [2], and tentatively confirmed to be so in a series of experimental studies of the past year [3,4,5]. I’ll discuss a simple model for a topological Kondo insulator and briefly introduce the most recent measurements, including ARPES , de Haas van Alphen and weak antilocalization that appear to support the idea that this is a strongly interacting topological insulator. One of the interesting questions is why the surface Dirac Cones seem to involve light fast electrons. I will discuss this in the context of “Kondo Band Bending”- the modification of the Kondo effect by the surface.

[1] Work supported by DOE grant DE-FG02-99ER45790.
[2] M. Dzero et al. Phys. Rev. Lett. 104, 106408 (2010).
[3] S. Wolgast et al, PRB 88 , 18, 180405, (2013).
[4] D. J. Kim et al, Sci. Rep. 3, 3150, (2013).
[5] G. Li et al, arXiv:1306.5221 (2013).
[6] S. Thomas et al. arXiv:1307.4133 (2014).
[7] V. Alexandrov & P. Coleman, arXiv:1403.6819 (2014).

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