Spin-Charge Locked Magneto-Transport and Mesoscopic Interference Phenomenain Topological Insulators

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Genuine mesoscopic interference effects acquire increased complexity in topological insulators, where coherent electronic conduction is based on topologically non-trivial helical surface states wrapping around a nominally insulating bulk. We plan to systematically investigate various aspects and phenomena of magneto-transport through ballistic and disordered topological insulators at mesoscopic scales with particular focus on the interplay between quantum coherence and topology. To this end will consider the following inter-related objectives: (i) Extending our promising studies from the first funding period we will address the limits and robustness of quantum spin Hall edge conductance in 2D structures with emphasis on the role of charge puddles due to long-range potential fluctuations. (ii) We will consider quantum interference effects, in particular Aharonov-Bohm-type features, in the magneto-conductance of 3D topological insulator nanowires and structures built from them. (iii) We will investigate the coupled charge and spin dynamics on the surface of 3D topological insulator nanostructures, with emphasis on non-local effects in multi-terminal configurations and the role of gating. In particular, we will explore, in view of spin-momentum locking, the consequences of spin injection/extraction via ferromagnetic contacts.On the one hand we will employ analytical techniques from the theory of mesoscopic conductors and on the other hand efficient numerical tight-binding transport codes for realistic models of HgTe-based topological insulators by taking into account disorder, spin-orbit interaction and electrostatic gating effects. We will perform our investigations in close cooperation with corresponding experiments on quantum transport in 2D and 3D topological insulators.