Metallicity at interphase boundaries due to polar catastrophe induced by charge density discontinuity

摘要

Tin oxide semiconductors can turn metallic at customized interfaces between two crystal phases, a theoretical study has found. Inspired by recent discoveries of surprisingly conductive regions formed when different insulators are sandwiched together, Udo Schwingenschlögl and two colleagues from KAUST in Saudi Arabia investigated whether similar properties could emerge at phase boundaries inside tin oxide materials. Density functional calculations of tin monoxide-dioxide interfaces indicate that certain polar arrangements generate desirable, high-mobility quantum gases even though the two sides of the boundary have the same formal charge – typically, abrupt charge changes are needed to create two-dimensional metallic states. The team proposed that this unexpected behavior arises from charge density discontinuities due to the mismatched lattices of tin monoxide and dioxide.