First-principles study of the electronic structure of CaKRu$_4$P$_4$

Abstract

The recent discovery and studies of 1144-phase compounds, e.g. CaKFe4As4, have attracted significant research interest. In this paper, based on the first-principles density functional calculations, we present a systematic study on the electronic structure of the recently synthetized 1144-type quaternary compound CaKRu4P4. We find that the Ru-based 1144-type compound possesses a different electronic structure from that of iron-based superconductors, even though they share very similar crystallographic structures. In CaKRu4P4, there is no hole-type carrier if spin-orbit interaction is not considered. And a long-range magnetic order is absent in its ground state. With the application of pressure, the electronic structure of CaKRu4P4 becomes similar to those of the ternary 122-type compounds LaRu2P2 and LaRu2As2. CaKRu4P4 is very likely to be a phonon-mediated medium coupled BCS superconductors. Furthermore, type-I and type-II Dirac fermions can be created and regulated in this system with pressure. The quaternary compound CaKRu4P4 therefore has a potential to be an attractive platform for the study of topological physics and superconductivity.