Semiconductors with a loop of extrema

Abstract

Crystals with a Wurtzite-type structure are used as an example to show that owing to spin–orbit coupling a new type of band structure can arise. For this band structure the extrema are reached at a circle, a loop of extrema, rather than in isolated points of the Brillouin zone. Specific properties of such semiconductors are studied theoretically, in particular, the peculiarities of the cyclotron resonance at low temperatures. In strong magnetic fields, spin–orbit coupling results in absorption at the frequency of electron spin resonance but driven by the electric vector of electromagnetic wave (combined resonance).