Switchable Atomically Thin 2D Electrides from First-principles Prediction

TL;DR

This paper predicts switchable 2D electrides with tunable electronic states, offering less reactive semiconductors that can transition to metallic states under strain, promising for quantum and electronic applications.

Contribution

The study introduces a new class of switchable 2D electrides with controllable NFE states, identified through high-throughput first-principles calculations, expanding potential applications.

Findings

Identified 12 candidate 2D electrides with low-energy NFE states.

Demonstrated strain-induced semiconductor-metal transition in Na₂Pd₃O₄.

Proposed switchable electrides as platforms for quantum phenomena and devices.

Abstract

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 with the environmental agents. In this work, we report the discovery of a group of two-dimensional (2D) moonolayer 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 partially occupied bands close to the Fermi level, the switchable electrides are chemically much less active semiconductors holding the NFE states that are 0.3-1.5 eV above the Fermi level. According to a high throughput search, we identified 12 2D candidates that possess such low-energy NFE states. Among them, 11 2D materials can likely be exfoliated from the known layered materials. Under external forces, such as a compressive strain, these NFE states stemming from the surface image potential will be pushed downward to cross the Fermi level. Remarkably, the critical semiconductor-metal transition can be achieved by a strain as low as 3% in 2D monolayer Na$_2$Pd$_3$O$_4$. As such, the switchable 2D electrides may provide an ideal platform for exploring novel quantum phenomena and modern electronic device applications.