Terahertz resistive response of a two-dimensional topological insulator in a quasiballistic transport regime

The terahertz resistive response of a two-dimensional topological insulator in a HgTe quantum well in the quasiballistic transport regime is studied. The photoresistance appearing only near the charge neutrality point is detected. The application of the magnetic field up to 4 T in the plane of the quantum well results in an increase in the photoresistance in the peak and in the expansion of the region near the charge neutrality point where it exists. The reported results imply that the observed photoresistance is due to transitions involving edge dispersion branches of the two-dimensional topological insulator