Fig. 2
Anisotropy of the photogalvanic effects in Bi2Se3. a Measurement scheme. The polarization of the incident light is changed by rotating a quarter waveplate with angle α. The Bi2Se3 is patterned to a circular disk. Nine pairs of electrodes are used to measure photocurrent generate along different directions when the sample is rotated with angle φ. b The lattice structure of the Bi2Se3 crystal showing threefold rotational symmetry along the z-axis. c Polarization-dependent photocurrent collected with electrode pair positioned along the y-axis when the sample is rotated to representative values of φ. d–g Parameters (C, L 1, L 2, D) extracted from the measurement in (c) as a function of φ. While L 2 and D show clear anisotropy with threefold rotational symmetry in agreement with the crystal structure of Bi2Se3, C and L 1 show no obvious angular dependence. The fitting errors for all the coefficients are very small and hence not shown here
