Is SmB₆ a topological Kondo insulator?

Kondo insulators mix local and itinerant states of opposite parity and can in this way give rise to topological insulator phases [1], as initially suggested for SmB₆ [2]. While SmB₆ exhibits a conductive surface at low temperatures with surface states at specific points in the Brillouin zone, the expected Dirac cone dispersion remains elusive. Hlawenka et al. [3] found the Γ-bar state to be topologically trivial. A surface-shifted hybridized 5d-4f dispersion at X-bar was also observed, explaining the surface metallicity despite the surface state's trivial nature [3]. The shift is consistent with STS [4,5]. Open questions remain regarding the spin polarization of surface states and umklapp features on the B-terminated surface. Recent discussions challenge the interpretation of the Γ-bar state, proposing a contour so far assigned to umklapp from the X-bar state as the missing Dirac cone necessary for SmB₆ to be topological [6-8]. This presentation addresses these questions.

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