Abstract:

Experiments show, and quantum physics explains, the emergence of two fundamental charged quasi-particles in crystalline solids, called band electrons and holes. While a band electron is very similar to an electron in vacuum, a hole is more like the bubble in a spirit level, i.e., it is a void in the electron liquid! In addition to carrying charge, band electrons and holes behave like tiny permanent magnets due to their spin. Crystal structure renders the spin of band electrons and holes to be very different. Holes are spin-3/2 particles and subject to a strong coupling between their spin and orbital motion. When holes are confined to move in nanometre-size electric circuits, this spin-orbit coupling causes intriguing effects that are never seen in similar structures made with band electrons. We have studied theoretically the interplay between quantum confinement of holes in wires and rings and their spin properties. In the wires, we find novel spin-polarisation states realised at quasi-1D subband edges, which can be probed in transport experiments. In hole rings, we show that the quantum-interference contribution to the two-terminal conductance exhibits an energy-dependent Aharonov-Anandan phase that is unrelated to Rashba or Dresselhaus spin splittings. Instead, confinement-induced heavy-hole - light-hole mixing is found to be the origin of this phase, which has ramifications for magneto-transport measurements in gated hole rings.
 
 
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