Strong electron correlation-induced Mott-insulating electrides of Ae5X3 (Ae = Ca, Sr, and Ba; X = As and Sb)

Abstract

The presence of interstitial electrons in electrides endows them with interesting attributes, such as low work function, high carrier concentration, and unique magnetic properties. Thorough knowledge and understanding of electrides are thus of both scientific and technological significance. Here, we employ first-principles calculations to investigate Mott-insulating Ae5X3 (Ae = Ca, Sr, and Ba; X = As and Sb) electrides with Mn5Si3-type structure, in which half-filled interstitial electrons serve as ions and are spin-polarized. The Mott-insulating property is induced by strong electron correlation between the nearest interstitial electrons, resulting in spin splitting and a separation between occupied and unoccupied states. The half-filled antiferromagnetic configuration and localization of the interstitial electrons are critical for the Mott-insulating properties of these materials. Compared with that in intermetallic electrides, the orbital hybridization between the half-filled interstitial electrons and the surrounding atoms is weak, leading to highly localized magnetic centers and pronounced correlation effects. Therefore, the Mott-insulating electrides Ae5X3 have very large indirect bandgaps (∼0.30 eV). In addition, high pressure is found to strengthen the strong correlation effects and enlarge the bandgap. The present results provide a deeper understanding of the formation mechanism of Mott-insulating electrides and provide guidance for the search for new strongly correlated electrides.

BaCu, a Two-Dimensional Electride with Cu Anions

“…As shown in Figure b and c, the interstitial electrons in Ba 6 octahedra are mainly distributed near the Fermi energy level, which is typical of anionic electrons, rather than the multicenter bonding states, as found in the Ca 4 tetrahedra of CaCu ( Pnma ) and Ca 2 Cu . In typical ionic electrides with p -block anions, the highly localized anionic electrons can form new bands around the Fermi level, e.g., Ba 5 Sb 3 , Sc 2 C, and Ca 2 N . Both conventional 2D materials and 2D electrides exhibit flat bands along specific high-symmetry K paths, such as Ca 2 N and YCl in L-A, due to the localized anionic electrons and weak interaction between adjacent layers.…”

Deviatoric stress-induced metallization, layer reconstruction and collapse of van der Waals bonded zirconium disulfide

“…Among the myriad candidates, transition metal dichalcogenides (TMDs) have drawn substantial attention due to their remarkable polymorphism and highly tunable band-gap structures. Their electronic structures were reported to span the entire range of solid states, encompassing Mott insulating 1 , 2 , semiconducting 3 , semimetallic to metallic 4 , and even superconducting states 5 , 6 . Such versatility of electronic property stems from their unique atomic arrangements, characterized by the stacking of sandwiched X-M-X monolayer (X: chalcogen, M: transition metal) interacted through weak van der Waals (vdW) forces 7 , 8 .…”