Cubic Topological Kondo Insulators

Abstract

Current theories of Kondo insulators employ the interaction of conduction electrons with localized Kramers doublets originating from a tetragonal crystalline environment, yet all Kondo insulators are cubic. Here we develop a theory of cubic topological Kondo insulators involving the interaction of Γ(8) spin quartets with a conduction sea. The spin quartets greatly increase the potential for strong topological insulators, entirely eliminating the weak topological phases from the diagram. We show that the relevant topological behavior in cubic Kondo insulators can only reside at the lower symmetry X or M points in the Brillouin zone, leading to three Dirac cones with heavy quasiparticles.

In-gap collective mode spectrum of the topological Kondo insulatorSmB6

“…The interest in SmB 6 and other Kondo insulators has been renewed recently by the realization that their bandstructure may have non-trivial topology [18][19][20][21][22] . As a putative strong topological insulator (TI), SmB 6 is expected to have a metallic crystal boundary protected against any source of backscattering that respects the time-reversal (TR) symmetry.…”

Nonuniversal weak antilocalization effect in cubic topological Kondo insulators

“…Interestingly, the Nernst effect data on the (011) plane reports the effective mass for the carries of the order of 100 of bare electron mass in agreement with existing theoretical estimates. 32,33 Observation of the weak anti-localization correction to conductivity in topological insulators generally serves as an indication of the strong-spin orbit coupling and, therefore, is used to confirm the helicity of the conducting surface states. In topological Kondo insulators, however, the analysis of the experimental data is complicated by the possibility of the conventional polar bands which will be split by the Bychkov-Rashba spin-orbit coupling λ SO .…”

“…On the other hand, these observations would contradict a natural expectation that the value of alpha must be close to α ≈ 3/2, which is due to the three Dirac bands on the surface of SmB 6 . 2,5,32,33 . Motivated by these experimental results, we calculate the quantum interference correction to conductivity in a generic cubic topological Kondo insulator.…”

Pressure-Driven Topological Phase Transition in the Yb Chalcogenides YbO and YbS

“…9 Their work showed that, with the fluctuating valence of a rare-earth element, the transition between topological trivial and nontrivial states can be realized in a simple cubic Kondo insulator prototyped using SmB 6 . 12 Both first-principles calculation and experiments suggest that the simple cubic SmB 6 with a mixed valence state is a candidate topological Kondo insulator (TKI). [15][16][17][18][19] PuB 6 is also predicted as candidate TKI by first-principles calculation.…”

“…[4][5][6][7] Not only conventional semiconductor materials with strong spin-orbital coupling (SOC), 8 but also Kondo insulator materials are attracting increasing research interest. [9][10][11][12][13][14] In 2010, on the basis of the periodic Anderson Kondo lattice model, Dzero et al proposed the topological classification in a simple cubic Kondo insulator. 9 Their work showed that, with the fluctuating valence of a rare-earth element, the transition between topological trivial and nontrivial states can be realized in a simple cubic Kondo insulator prototyped using SmB 6 .…”