Talk Title: Competing weak anti-localization and weak localization in topological insulators A magnetoconductivity formula is presented for the surface states of a magnetically doped topological insulator [1]. It reveals a competing effect of weak localization (WL) and weak anti-localization (WAL) in quantum diffusion transport when an energy gap is opened at the Dirac point by the magnetic doping. It is found that, while random magnetic scattering always drives the system from the symplectic to the unitary class, the gap could induce crossover from the weak anti-localization to the weak localization, tunable by the Fermi energy or the gap. We not only described the crossover from WAL to unitary [2], but also predicted the recent experimental progress that observed the crossover from WAL to WL [3]. The possible role played by the bulk states in the observed weak antilocalization in recent experiments will also be discussed. References: [1] "Competing weak localization and anti-localization in topological surface states", Hai-Zhou Lu, Junren Shi, and Shun-Qing Shen, arXiv:1101.5437 (2011). [2] "Impurity effect on weak anti-localization in the topological insulator Bi2Te3", Hong-Tao He, Gan Wang, Tao Zhang, Iam-Keong Sou, George K. L. Wong, Jian-Nong Wang, Hai-Zhou Lu, Shun-Qing Shen, Fu-Chun Zhang, Phys. Rev. Lett. 106, 166805 (2011). [3] "Crossover between weak localization and weak antilocalization in magnetically doped topological insulator", Minhao Liu, Jinsong Zhang, Cui-Zu Chang, Zuocheng Zhang, Xiao Feng, Kang Li, Ke He, Li-li Wang, Xi Chen, Xi Dai, Zhong Fang, Qi-Kun Xue, Xucun Ma, Yayu Wang, arXiv:1103.3353 (2011). |