Fig. 2: Observation of electric SHG under zero magnetic field in Bi2Se3.
From: Quantum frequency doubling in the topological insulator Bi2Se3
a Schematic illustration of the nonlinear transport measurements in a Hall bar device using the second harmonic method. b The second harmonic transverse voltage \({{V}}_{{y}}^{2{\omega}}\) versus ac current amplitude I in 20 QL Bi2Se3 at 50āK. The solid line is a quadratic fit to the data. Blue hexagon in the inset represent the FS of Bi2Se3. Red line is along the \(\overline \Gamma \overline K\) direction, and the black arrow denotes the current direction in k-space. c The second harmonic transverse resistance \({{R}}_{{{yx}}}^{2{\omega}}\) scales linearly with I at 50āK. It changes sign with reversing the current direction and corresponding Hall probes. d The \({{R}}_{{{yx}}}^{2{\omega}}\left( {{I}} \right)\) curves measured at different temperatures from 20 to 200āK. e The slope of \({{R}}_{{{yx}}}^{2{\omega}}\left( {{I}} \right)\) curves \(\left( {{{R}}_{{{yxx}}}^{\left( 2 \right)}} \right)\) as a function of temperature. Error bars correspond to the standard error of linear fitting. f The measured carrier mobility Ī¼ as a function of temperature.
