Unusual Linear Magnetoresistance in Non-Metallic Topological Insulator Bi$_{2}$Te$_{3}$

ARPES experiments have shown that, in both Be$_{2}$Se$_{3}$ and Bi$_{2}$Te$_{3}$, the energy gap is crossed by a single surface state (SS) with Dirac-like dispersion [1,2]. Spin-resolved ARPES [1] shows that the spin of the SS has a Rashba-like coupling, consistent with the identification of these materials as topological insulators. To explore the surface-state transport properties in Bi$_{2}$Te$_{3}$, we have examined in detail the low-temperature ($T)$ transport properties in crystals with non-metallic \textit{$\rho $} vs. $T$ profiles. At 0.3 K, we observe an unusual $H$-linear magnetoresistance (MR) that extends in field $H$ from 0.05 T to 14 T. The $H$-linear dependence is observed with \textbf{H} $\vert \vert $ \textbf{c} and \textbf{H} in-plane. We discuss a scenario in which the $H$-linear MR arises from the effect of \textbf{H} on the spins of the carriers in the topological SS. We also discuss a comparison with $H$-linear MR in Bi$_{1-x}$Sb$_{x}$. \\[4pt] [1] Y. Xia \textit{et al}., Nat. Phys. \textbf{5}, 398 (2009). \\[0pt] [2] Y. L. Chen \textit{et al}., Science, \textbf{325}, 178 (2009).