CAREER: Mesoscopic spin-dependent transport

1. CAREER: Mesoscopic spin-dependent transport in two-dimensional systemsJean J. Heremans, Virginia TechDMR-0618235 We study electronic phenomena in narrow-gap semiconductors such as InSb and InAs, where spin-orbit interaction is strong. The spin-orbit interaction allows us to investigate structures where the electron’s quantum-mechanical spin can be used to modify the electronic transport properties. These devices need to be small, of length scales comparable to the electron mean-free-path and the spin coherence length. The upper figure shows data on a transverse magnetic focusing geometry in InSb, which replicates a mass spectrometer, as the inset shows (with typical electron orbits). But instead of filtering by mass, this device filters by spin, using the fact that electrons with different spin states follow different orbits under a magnetic field. The lower figure shows data obtained on an interferometer in InSb, depicted in the inset with a typical orbit. The data represent quantum-mechanical Altshuler-Aronov-Spivak oscillations. The oscillations contain spin-dependent information, and are used to calculate the spin coherence length. magnetic field (T) magnetic field (T)

2. CAREER: Mesoscopic spin-dependent transport in two-dimensional systemsJean J. Heremans, Virginia TechDMR-0618235 Education: One post-doc (Hong Chen, since 08/06 a faculty member at the University of North Florida), two graduate students (John Peters, Yue Pan) and several undergraduate students contributed to the research. We mention undergraduate REU student Jonas Beardsley (Ohio University) who built a variable temperature system with a cryogenic cooler (picture below), and acquired data. Further, a cooperative education program was started with a two-year technical college. Societal impact: Two current research developments in electronics show substantial promise: nanoscale electronics, and electronics utilizing the electron’s quantum-mechanical spin, rather than only charge to convey information. The present research examines the effect of spin on the electronic properties of nanoscale devices, merging these two developments. The results have implications for knowledge in basic science, but can also be utilized to define the parameters important to ultimately create a spin transistor. REU student Jonas Beardsley in front of his magnetotransport system