Interactions between the surface and the bulk in a topological insulator (TI) cause a finite quasiparticle lifetime of the topological surface states (TSS) as shown by the recent experiments for Bi2X3 (X=Se,Te). Previously, hexagonally warped topological band has been detected and other anomalies related to warping have been reported. The most remarkable among which is the 6-fold periodic spin canting anomaly (SCA) of the in-plane spin around the spin-1/2 vortex.

This talk is focused on understanding this SCA from an interaction point of view between the TSS and the bulk. We first device a general scheme based on interactions and the spin-off-diagonal component of the self energy. It is shown that, the spin-off diagonal interaction channel is topology preserving. Then the effective interaction strength, strong spin-orbit coupling and the Fermi surface warping is shown to cooperate in giving rise to the periodic spin canting anomaly. Our result points at the presence of the topology friendly interaction channels in strong TIs.

КАК ПОПАСТЬ НА СЕМИНАР: На физфаке МГУ пропускной режим, желательно иметь с собой паспорт. Организаторы встретят участников. Телефон организатора: +7-911-703-2266 (Михаил Евгеньевич Журавлев).

We develop the theory of transverse magnetoresistance in layered quasi-two-dimensional metals. Using the Kubo formula and harmonic expansion we calculate intralayer conductivity in a magnetic field perpendicular to conducting layers. The analytical expressions for the amplitudes and phases of magnetic quantum oscillations (MQO) and of the so-called slow oscillations (SlO) are derived and applied to analyze their behavior as a function of several parameters: magnetic field strength, interlayer transfer integral and the Landau-level width. Both the MQO and SlO of intralayer and interlayer conductivity have approximately opposite phase in weak magnetic field and the same phase in strong field. The amplitude of SlO of intralayer conductivity changes sign at $\omega_c\tau\approx\sqrt{3}$. There are several other qualitative differences between magnetic oscillations of in-plane and out-of-plane conductivity. The results obtained are useful to analyze experimental data on magnetoresistance oscillations in various strongly anisotropic quasi-2D metals.