Experimental Physics III

Quantum Transport

The research area of the Quantum Transport group is the experimental investigation of quantum phenomena in the transport properties of nano-structured semiconductor materials.

Currently the research is focused on the transport properties of topological insulators and related meterials which are realised in HgTe quantum well and bulk materials.

Topological Insulators (TI)

Topological insulators (TI) are a new class of materials which consits of an insulating bulk and metallic surface states. In contrast to ordinary surface states the surface states of a TI are protected by time reversal symmetry. These surface states exhibit distinct spin properties and back scattering becomes suppressed.

The TI state was first experimentally observed by our group in a two-dimensional (2D) electron system of a HgTe quantum well (QW). In case of a 2D system the surface states are counter-propagating one-dimensional (1D) channel with opposite spin polarisation (see figure).
The dissipationless spin transport properties of such structures are subject of intens experimental investigations.

HgTe 2D and 3D TI are grown within the QT group by molecular beam epitaxy (MBE).
Nano- and micro-structures are fabricated by optical and electron-beam lithography using the nano-structuring facilities of the Lehrstuhl EP3.
Transport characterization measurements are done in the temperature range between 5 mK and room temperature and in magneic fields up to 18 T.