Influence of device geometry and imperfections on the interpretation of transverse magnetic focusing experiments

TL;DR

This paper investigates how device geometry, lead shape, and disorder influence the interpretation of transverse magnetic focusing experiments used to separate spins in spintronics, emphasizing the importance of careful device design.

Contribution

It demonstrates that lead geometry and disorder significantly affect conductance spectra, highlighting the need for precise device characterization in spin separation experiments.

Findings

Lead shape and separation impact spectral feature resolution.

Number of subbands influences spin-split peak amplitudes.

Device disorder affects the reliability of focusing measurements.

Abstract

Spatially separating electrons of different spins and efficiently generating spin currents are crucial steps towards building practical spintronics devices. Transverse magnetic focusing is a potential technique to accomplish both those tasks. In a material where there is significant Rashba spin--orbit interaction, electrons of different spins will traverse different paths in the presence of an external magnetic field. Experiments have demonstrated the viability of this technique by measuring conductance spectra that indicate the separation of spin-up and spin-down electrons. However the effect that the geometry of the leads has on these measurements is not well understood. We show that the resolution of features in the conductance spectra is affected by the shape, separation and width of the leads. Furthermore, the number of subbands occupied by the electrons in the leads affects the ratio between the amplitudes of the spin-split peaks in the spectra. We simulated devices with random onsite potentials and observed that transverse magnetic focusing devices are sensitive to disorder. Ultimately we show that careful choice and characterisation of device geometry is crucial for correctly interpreting the results of transverse magnetic focusing experiments.