Research progress about 111-typed iron based superconductor

Abstract

111-typed iron based superconductors have three members: LiFeAs, NaFeAs and LiFeP. The family of LiFeAs itself does not show any long range magnetic order but become superconductor without chemical doping. NaFeAs displays the separation of structural and magnetic transition, suitable to investigate the origin of the two transitions. LiFeP has been proved to be a nodal superconductor. The structure of 111 compounds consists of[FeAs/P] layers intercalated with two alkali metal layers, which makes single crystals easy to be cleaved into two equal counterparts with non-polar surface and thus is favored by the surface characterization techniques, such as the research of angleresolved photoemission experiment and scanning tunneling microscope measurement. Up to now, fruitful results have been achieved about the study of 111 family. In this paper, we summarize recent progresses on this family.