A. Kandala, A. Richardella, D. W. Rench, D. M. Zhang, T. C. Flanagan, N. Samarth
We develop hybrid ferromagnetic insulator (GdN)/topological insulator (Bi_2Se_3) heterostructure devices to probe the effects of broken time reversal symmetry on electrical transport in the surface states of a three dimensional topological insulator. Low temperature (0.28 K \leq T \leq 30 K) measurements of electrical transport in laterally patterned devices show that interfacing Bi_2Se_3 with ferromagnetic GdN yields distinctive signatures in the quantum corrections to the longitudinal magnetoconductance, clearly differing from the standard weak anti-localization seen in control channels of Bi_2Se_3. The absence of electrical transport in the insulating ferromagnetic GdN overlayer allows us to attribute these signatures to contributions from surface state transport in Bi_2Se_3. We show that the observations are consistent with the opening of a magnetic gap in the surface state spectrum due to broken time-reversal symmetry.
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http://arxiv.org/abs/1212.1225
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