Figure 1. Device configuration and dual-gated field effect at zero and low magnetic field.

(a) Device schematic. Inset is an optical microscope image of a typical dual-gated BSTS device before depositing the top-gate metal; Scale bar, 10 μm. (b,c) show 2D maps of ρ_xx at B=0 T and ρ_xy at B=1 T as functions of V_tg and V_bg on sample A. The blue (red) dashed lines in b are guides to the eye for the top (bottom) surface DP. The 2D map is generated by data measured from V_tg-sweeps at a series of V_bg values, with one example at V_bg=3 V shown in the inset of c. (d) Zero-magnetic-field minimum conductivity σ_min (bottom axis) measured in six dual-gated samples at low temperature (<2 K) plotted as a function of the sample thickness (data in circles) and 2D aspect ratio (L/W, data in squares). The vertical dashed line indicates 3.8e²/h.