Multi‐Dimensional Topological Fermions in Electrides

Abstract

Topological electrides have attracted extensive attention in various fields, for example, electrocatalysis, spintronics, electron emitters, etc., due to their non-trivial topological surface states and unique electronic properties. It is well known that topologically protected nontrivial surface states are not broken by external perturbations and further exhibit high carrier mobility and high electron density on some specific surfaces. In addition, electrides usually possess a lower work function due to the presence of approximately loose excess electrons. In this case, topological electrides not only build a bridge between topological materials and electrides, but also couple various excellent properties of these two materials. Since the concept of topological electrides was first proposed, several novel types of topological electrides have been reported in the last few years. Therefore, it is necessary to give a comprehensive review of these topological electrides. In this review, the history of the development of topological electrides and their current status is systematically summarized. In addition, relevant insights into the challenges and opportunities facing topological materials are provided.

Multi-dimensional inorganic electrides for energy conversion and storage

“…87–91 These potential applications of topological materials are precisely due to the presence of “robust surface band structures”. Currently, based on the dimensions of degenerate bands, TSMs can be classified into nodal point semimetals (two (Weyl) -/triple-/four (Dirac) -/six-/eight-fold degenerate points), nodal line semimetals, and nodal surface semimetals, 92–99 as shown in Fig. 5a.…”

“…Since then, researchers have discovered multiple types of topological electrides, including Dirac electride Ca 3 Pb, 7 ferromagnetic nodal line electride Gd 2 C, 8 0D electrides Li 12 Mg 3 Si 4 /C12A7:e − with a six-fold degenerate point, 46,98 Ba 4 Al 5 with multiple topological states (namely Weyl points, nodal lines, and nodal surfaces), 62 nodal surface electrides Ba/Sr 3 MnN 3 , 65 Dirac nodal line electride Ba 3 N, 66 etc. In 2023, our team 99 carried out a comprehensive review of the development and current status of topological electrides, as shown in Fig. 6a.…”

Weyl nodal lines, Weyl points and the tunable quantum anomalous Hall effect in two-dimensional multiferroic metal oxynitride: Tl2NO2

“…Two-dimensional (2D) multiferroics and quantum topological phases are two fascinating research topics in condensed matter physics 1–6 that have been attracting significant research interest. Symmetry plays a crucial role in investigating these two fields.…”