Surface Conductivity of the Ytterbium-Doped Topological Kondo-Insulator SmB 6

The temperature dependence of the conductivity of the topological Kondo-insulator (TKI) Sm 1 – x Yb x B 6 is investigated in the temperature range 2 < T < 300 K for compositions with x ≤ 0.024. It is found that the ytterbium impurity most strongly affects the low-temperature ( T < 20 K) electrical conductivity: when changing from x = 0 to x = 0.024, the activation energy of bulk conductivity decreases by 1.8 times from 4 to 2.2 meV, and the 2D surface conductivity increases by six times. The separation made for the contributions to the conductivity enables us to establish that the one-parameter scaling model can be used for describing the conductivity of 2D surface states in the Sm 1 – x Yb x B 6 TKI in which both the interaction with phonons and the electron–electron scattering effects are taken into account.