Symmetry, Anisotropy and Dimensionality: Spin physics in the elemental semiconductors Si, Ge, and P
By the 1980s, an accumulation of decades of research on charge transport in the elemental semiconductors silicon and germanium led to a lingering perception that there was nothing left for condensed matter physics to do with them. However, just before arriving at UMD almost 7 years ago, my lab demonstrated that these "old dogs" could be taught a few more "new tricks": Basic research on charge dynamics in these electronic materials eventually led to scores of real-life device applications, but spin dynamics remained unexplored. We figured out how to overcome several experimental challenges to inject spin-polarized electrons into these otherwise-nonmagnetic materials, and detect their remaining non-equilibrium spin orientation after traveling over amazingly long distances. In this talk, I will describe some of our many recent breakthroughs enabled by unique experimental capabilities and thorough theoretical understanding of both intrinsic and extrinsic phenomena dominating spin transport in Si and Ge. Furthermore, these two examples are not the end of the story, as new research moves forward into the spin physics of 2D elemental semiconductors like single-layer black phosphorus, or 'phosphorene'.