Anomalous Aharonov-Bohm Conductance Oscillations from Topological Insulator Surface States*

We study Aharonov-Bohm (AB) conductance oscillations arising from the surface states of a topological insulator nanowire, when a magnetic field is applied along its length. With strong surface disorder, these oscillations are predicted to have a component with anomalous period $\Phi_{0}=hc/e$, twice the conventional period. The conductance maxima are achieved at odd multiples of $\Phi_{0}/2$, implying that a $\pi$ AB phase for electrons strengthens the metallic nature of surface states. This effect is special to topological insulators, and serves as a defining transport property. A key ingredient, the surface curvature induced Berry phase, is emphasized here. We discuss similarities and differences from recent experiments on $Bi_{2}Se_{3}$ nanoribbons, and optimal conditions for observing this effect.