Selective Switching Between Two Band-Edge Alignments in Ternary Pentagonal CdSeTe Monolayer: Atom-Valley Locking

In the field of photocatalytic water splitting, no current studies have explicitly investigated the coexistence of multiple band-edge alignments in two-dimensional (2D) materials with intrinsic electric fields. In this Letter, we designed the ternary pentagonal CdSeTe monolayer, and proposed a novel concept called atom-valley locking, which could provide multiple band-edge positions. In the CdSeTe monolayer, two distinct valleys emerge in the electronic structure, one contributed by Se atoms and the other by Te atoms, with a spontaneous polarization of 187 meV between them. This phenomenon can be attributed to the localization of valley electrons and the breaking of four-fold rotational reflection symmetry, yet it does not rely on the breaking of time-reversal symmetry. Due to the atom-dependent valley distribution, two types of band-edge alignments can be identified. Moreover, selective switching between them can be achieved by strain engineering, thereby enabling precise control over the site of the hydrogen evolution reaction. Our findings open up new opportunities for exploring valley polarization and provide unique insights into the photocatalytic applications of 2D materials with intrinsic electric fields.