We measure the temperature-dependent carrier density and resistivity of the topological surface state of thin exfoliated ${\mathrm{Bi}}_2{\mathrm{Se}}_3$ in the absence of bulk conduction. When the gate-tuned chemical potential is near or below the Dirac point, the carrier density is strongly temperature-dependent, reflecting thermal activation from the nearby bulk valence band, while, above the Dirac point, unipolar $n$-type surface conduction is observed with negligible thermal activation of bulk carriers. In this regime, linear resistivity vs temperature reflects intrinsic electron-acoustic phonon scattering. A quantitative comparison with a theoretical transport calculation including both phonon and disorder effects gives the ratio of deformation potential to Fermi velocity $D/\hslash {\nu }_{\mathrm{F}}=4.7{\AA }^{-1}$. This strong phonon scattering in the ${\mathrm{Bi}}_2{\mathrm{Se}}_3$ surface state gives intrinsic limits for the conductivity and charge carrier mobility at room temperature of $\sim 550\mu \mathrm{S}$ per surface and $\sim 10000{\mathrm{cm}}^2/\mathrm{V}\mathrm{s}$.

• Received 25 May 2012

DOI:https://doi.org/10.1103/PhysRevLett.109.166801