Adapted from Chong et. al. (2019) Physical Review Letters
In the presence of the magnetic field, a checkerboard pattern emerged from the metallic surfaces on the 3-D topological insulator devices (left and right columns correspond to longitudinal and transverse conductivities versus voltages on the two gates; TI thickness reduces going from top to bottom). These checkerboards allow the researchers to track any distortion on the surface. Thinner insulator layers showed a distorted pattern and at 16 nanometers thickness, the intersection points began to break up. This created a gap that indicated that the surfaces were no longer conductive.