The Unusual Properties of Spin-3/2 Holes in Gallium-Arsenide Semiconductor Nanostructures

Prof. Alex Hamilton

School of Physics, University of New South Wales

3:30 pm Wednesday, 15 September 2010,
EN101 (EN Building), Hawthorn.

The electrical current In a semiconductor can be carried by negatively charged electrons or positively charged holes. In undergraduate physics, we are often taught that holes in the valence band are just an absence of an electron. But they aren't. Valence band holes are spin-3/2 particles, and this gives them very different properties to spin-1/2 electrons. In recent years there has been growing theoretical interest in the possibility of using holes in semiconductor nanostructures for applications ranging from ultra-fast spin transistors through to quantum information and communication. This talk will describe where holes come from, why they are so different to electrons, and what one can do with holes that can't be done with electrons.

I will present new techniques we have developed for making p-type semiconductor nanostructures, and show electrical measurements of the first high quality hole quantum wires and dots. In quantum dots we can observe effects associated with the transport of single holes. In quantum wires the interplay of spin-orbit interaction and electrostatic confinement leads to an extreme anisotropy of the Zeeman spin-splitting that is completely unlike electrons. Confusingly the measured anisotropy is opposite to that predicted by the best available theory.

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