Electrides, with excess anionic electrons confined in their empty space, are promising for uses in catalysis, nonlinear optics, and spin electronics. However, the application of electrides is limited by their high chemical reactivity. In this paper, we report a group of chemically stable monolayer electrides with the presence of switchable nearly free electron (NFE) states in their electronic structures. Unlike conventional electrides, which are metals with floating electrons forming the bands crossing the Fermi level, the switchable electrides are semiconductors holding the NFE states close to the Fermi level. According to a high-throughput search, we identified 11 candidate materials with low-energy NFE states that can likely be exfoliated from the known layered materials. Under external strain, these NFE states, stemming from the surface image potential, will be pushed downward to cross the Fermi level. The critical semiconductor-metal transition can be achieved by a strain within 10% in several monolayer materials. These switchable electrides may provide an ideal platform for exploring quantum phenomena and modern electronic device applications.

• Received 4 September 2020
• Accepted 17 February 2021

DOI:https://doi.org/10.1103/PhysRevB.103.125103