Birefringent Spin Polarized Electron Optics in Ballistic Nano-Devices

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Rashba spin-orbit interaction is one of the most promising effects for the creation and manipulation of spin polarizations in low-dimensional electronic semiconductor systems without using external magnetic fields or magnetic materials. Since the introduction of the spin field-effect transistor by Datta and Das in 1990 many theoretical ideas have been published. In this project we explore, theoretically and experimentally, the concepts of spin electron optics in ballistic two-dimensional electron and hole systems. HgTe nanostructures, which exhibit a strong Rashba-type spin-orbit interaction, are the basis for our studies. Quantum point contacts are used for ballistic electron injection and detection while the propagation direction of spin polarized carriers is manipulated by the gate controllable Rashba spin-orbit coupling strength. The underlying effect is the electronic analogue of the birefringence properties of optically active polarizing materials. Theoretically, the electron beam propagation and manipulation is described by the so called Landauer-Büttiker-Keldysh formalism. We will look for the efficiency of electron-beam polarization and novel spin-interference effects which can emerge from the complex band structure of HgTe nanostructures.