Tunable Topological State, High Hole-Carrier Mobility, and Prominent Sunlight Absorbance in Monolayered Calcium Triarsenide

摘要

Designing novel two-dimensional (2D) materials is highly desirable for material innovation. Here, we propose monolayered calcium triarsenide (1L CaAs_(3)) as a new 2D semiconductor with a series of encouraging functionalities. In contrast to the ～33 meV small band gap in bulk CaAs_(3), 1L CaAs_(3) possesses a large direct band gap of 0.92 eV with a high hole mobility of ～10~(4) cm~(2) V~(–1) s~(–1). The electronic properties of 2D CaAs_(3) can be manipulated significantly by the layer thickness and external strains. Remarkably, 2D CaAs_(3) suggests a topologically nontrivial–trivial state transition under thickness reduction and strain engineering, which is attributed to the drastic surface relaxation and pinch effect under compression. A semiconductor–semimetal transition is also revealed when the layer thickness is greater than 3L. Furthermore, 1L CaAs_(3) exhibits prominent visible-light absorption compared with the crystalline silicon. All these desired properties render 2D CaAs_(3) a promising candidate for use in electronic and photovoltaic devices.