Superconducting state of excitonic insulator

摘要

A state of an excitonic insulator with the electric current is studied.Initially, in the metallic phase, the electrons and holes are assumed to bemoving in the opposite directions, so as the electric current exists. Thisstate is supported by an external condition (the specimen is in an electriccircuit with the current). When the temperature decreases, the transition tothe ordering state due to formation of the electron--hole pairs is possible(similar to the ordinary state of the excitonic insulator). The properties ofthe state at zero temperature are investigated. The spectrum of elementaryexcitations has a gap, and so the conclusion can be made that obtained state issuperconducting one. Thus, depending on the external conditions, excitonicinsulator behaves itself like the insulator or superconductor. That is correctin the limit of strong overlapping of the electron--hole pairs.