Quantum layertronics in van der Waals systems

In van der Waals systems, the interlayer van der Waals coupling between adjacent atomically thin layers renders the electronic wave function to reside on more than one specific layer, promoting the layer degree of freedom from a spatial object to a quantum mechanical pseudospin. The coupling of layer degree of freedom with the in-plane center-of-mass motion of electrons shapes nontrivial layer pseudospin structures in momentum space, leading to various new quantum geometric properties in an extended parameter space unique to lattice mismatched van der Waals systems. They underly a plenty of novel transport and optical effects, linear and nonlinear responses, and offer new pathways towards device applications, constituting the research frontiers of quantum layertronics. This article provided a brief review of this emerging research direction, and discussed possible developments in near future based on its crossings with other intensive research fields such as nonlinear electronics, twistronics and chiral electronics.