Abstract

Spin-orbit coupling can lead to many interesting effects, such as the spin-Hall effect, Edelstein effect, topological insulators, and Majorana fermions. I will discuss what appears to be a novel effect in spin-orbit coupled systems. Disordered alloys of gold and germanium show weak anti-localisation (WAL) when the magnetic field is varied quasistically, as is expected with a spin-orbit coupled system. However, the magnetoresistance changes dramatically when the field is swept at a constant non-zero rate, with the resistance depending on both the sweep rate and the direction of the sweep. These non-equilibrium resistance values are long-lived, taking tens of seconds to revert to the equilibrium resistance. Intriguingly, this behaviour is only seen in AC measurements, not in DC measurements. Similar results have been seen in other systems with spin-orbit coupling. I will discuss these results, ruling out several possible explanations. Finally, I will introduce a simple model which captures the main features of the experimental results using the nature of the band structure in spin-orbit coupled materials.