Project QuMat.1-UT-1.1D / 1.2D in Pillar 1

Devices based on quantum spin Hall insulator/X hybrids

Successful Bi-based hetero-materials will be incorporated in Hall-bar type devices. We will investigate the transport properties of the quantum channels in terms of their quantum conductivity, robustness against temperature and magnetic fields and scatterers. Such devices are of interest in their own right, but they also form the first stage of devices with superconductive edge channels and spin-filtering developed in other research projects (pillars 2,3).

Optimized materials with a strong topological gap will be incorporated into a gated Hall bar device. We will characterize the overall charge transport by having a single contact feeding current at the same time to the top and bottom edges (the source-drain bias is measured separately). In addition, we will develop devices in which selectively only one edge channel is fed, thus addressing a single specific spin mode at this edge. This allows us to investigate the degree of spin filtering provided by a single helical spin mode. The coherence pathlengths for the charge- and spin quantum states will be measured and potential sources of decoherence (scattering and nuclear magnetic centers) will be investigated. The final goal is to maximize the spin coherence length in ultra-pure and isotopically well-defined systems.