S devices

The surfaces of three dimensional topological insulators are two dimensional electron gases of Dirac fermions without electron-phonon scattering contamination. In the quantum Hall states of the surface states system, the mechanism of transport dispassion change from thermal activation to the variable range hopping at a critical temperature 20K. The quantum Hall plateau-to-plateau transition behavior in the temperature regime below 20K gives with a universal exponent k=0.20 . It indicates that only electron-electron interaction dominates the inelastic scattering mechanism in the two dimensional topological electron system.