Fingerprints of Inelastic Transport at the Surface of the Topological InsulatorBi2Se3: Role of Electron-Phonon Coupling

We report on electric-field and temperature-dependent transport measurements in exfoliated thin crystals of the ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ topological insulator. At low temperatures ($<50\text{ }\text{ }\mathrm{K}$) and when the chemical potential lies inside the bulk gap, the crystal resistivity is strongly temperature dependent, reflecting inelastic scattering due to the thermal activation of optical phonons. A linear increase of the current with voltage is obtained up to a threshold value at which current saturation takes place. We show that the activated behavior, the voltage threshold, and the saturation current can all be quantitatively explained by considering a single optical-phonon mode with energy $$\hbar${}\mathrm{$\Omega${}}$\approx${}8\text{ }\text{ }\mathrm{meV}$. This phonon mode strongly interacts with the surface states of the material and represents the dominant source of scattering at the surface at high electric fields.