Bismuth selenide
Bismuth selenide is a gray compound of bismuth and selenium also known as bismuth selenide. It is a semiconductor and a thermoelectric material. In its pure state it has a topological insulator ground-state. While perfect stoichiometric bismuth selenide should be a semiconductor naturally occurring selenium vacancies act as electron donors and it often acts as a semimetal in its as grown phase. Topologically protected Dirac cone surface states have been observed in Bismuth selenide and its insulating derivatives leading to intrinsic topological insulators, which later became the subject of world-wide scientific research.
