Fig. 2: Valley-dependent topological phase transitions in VSi2N4.
From: Sign-reversible valley-dependent Berry phase effects in 2D valley-half-semiconductors
a, b The top and side views of MA2Z4 materials family. The dashed lines in (a) indicate the 2D primitive cell. c The Brillouin zone of MA2Z4. d The band structures of VSi2N4 were calculated by the hybrid functional without SOC (left panel) and with SOC (right panel). (e) The stress-strain curve of VSi2N4. The top x-axis plots the whole strain range of 0–30%, while the bottom x-axis plots the small strain range of 0–3%. The colors indicate the magnitudes of the bandgap, and the corresponding Chern number (\({{{\mathcal{C}}}}\)) is marked. The evolution of band structure (f) and orbital compositions at band edge (g) under the strain of 0–2%. Various fully spin-polarized valley topological states emerge, including VHSC (0%), VHSM (1.4%), VQAH (1.6%), VHSM (1.75%), and VHSC (2%).
