  Manipulating valley-dependent Berry phase effects provides remarkable
opportunities for both fundamental research and practical applications. Here,
by referring to effective model analysis, we propose a general scheme for
realizing topological magneto-valley phase transitions. More importantly, by
using valley-half-semiconducting VSi2N4 as an outstanding example, we
investigate sign change of valley-dependent Berry phase effects which drive the
change-in-sign valley anomalous transport characteristics via external means
such as biaxial strain, electric field, and correlation effects. As a result,
this gives rise to quantized versions of valley anomalous transport phenomena.
Our findings not only uncover a general framework to control valley degree of
freedom, but also motivate further research in the direction of multifunctional
quantum devices in valleytronics and spintronics.
