Single-edge transport in an InAs/GaSb quantum spin Hall insulator

We report transport measurements in a single edge channel of an InAs/GaSb quantum spin Hall insulator, where the conduction occurs through only one pair of counterpropagating edge modes. By using a specific sample design involving highly asymmetric current paths, we electrically isolate a single edge channel of the two-dimensional topological insulator from the other edge. This enables us to probe a single edge by multiterminal measurements. Both two-terminal and four-terminal resistances show a nearly quantized plateau around $h/e^2$ for a 4-$\mu$m-long edge, indicating quasiballistic transport. Our approach is advantageous in that it allows us to gain insight into a microscopic region from local measurements.