Figure 4
(a) Measured logarithmic temperature-dependent conductivity for Bi2Se3 thin films at low temperature. The red solid lines are guides for the eye. (b) Measured logarithmic temperature-dependent conductivity of a representative thin film with the t = 9 nm at perpendicular magnetic field which increases from 0 to 2 T by a step of 0.2 T. The solid lines are a guide for the eye. Inset: slope κ = (πh/e2)(∂σ/∂ln T) obtained by linear fitting the curves in main panel of (b) plotted as a function of magnetic field. (c) Variation of 
at 2 T with temperature for different thicknesses. (d) Comparison between the extracted α and κee as a function of t. Two red dashed horizontals mark two κee corresponding to n = 1 and n = 3, respectively.
