Exotic phenomenon can be achieved in quantum materials by confining electronic states into two dimensions. For example, quantized Hall effect can be resulted in a unit cell of a periodic 2D system (Nobel prize in 1988), relativistic fermions are realized in a single layer of carbon atoms arranged in a two-dimensional (2D) honeycomb lattice while such electronic state is absent in the bulk graphite (Nobel prize in 2010), superconducting transition temperature can be enhanced by confining materials into 2D, and so on. Ordinarily, the 2D electronic system can be artificially created by exfoliating the layered materials, growing on substrates via molecular beam epitaxy, or building interfaces between two different materials. Searching for new methods to confine electronic states into 2D is important in condensed matter physics.