Figure 4. Weak anti-localization (WAL) effect in BST crystal.

(a) The change of sheet magnetoconductance plotted in the perpendicular magnetic field component of the magnetic field, Bsinθ, at 1.9 K. The only perpendicular component dependent features indicate that WAL is induced by 2D surface electrons. (b) The change of sheet magnetoconductance (ΔG_xx) in perpendicular magnetic fields (θ = 90°) at temperatures ranging from 1.9 to 30 K. It shows the WAL features (sharp cusps at around zero magnetic field) persistent until 10 K. (c) Trace of sheet magnetoconductance's change at 1.9 K, the solid lines (red) are fits of 2D localization theory, where α is -0.56, and is 318 nm, confirming the 2D nature of WAL. (d) Temperature dependence of phase coherent length L_φ obtained by fitting ΔG_xx to 2D localization theory. The solid line (red) shows the power law dependence of temperature as ∼T^−0.44.