2020 5th International Seminar on Advances in Materials Science and Engineering
Zhiming Yu

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Prof. Zhiming Yu

Beijing Institute of Technology


Reaeach area :

topological semimetal; Valleytronic; Anomalous spatial shift


Speech title:

Valley-Layer Coupling: A New Design Principle for Valleytronics


Abstract:

The current valleytronics research is based on the paradigm of time-reversal-connected valleys in twodimensional (2D) hexagonal materials, which forbids the fully electric generation of valley polarization by a gate field. Here, we go beyond the existing paradigm to explore 2D systems with a novel valley-layer coupling (VLC) mechanism, where the electronic states in the emergent valleys have a valley-contrasted layer polarization. The VLC enables a direct coupling between a valley and a gate electric field. We analyze the symmetry requirements for a system to host VLC, demonstrate our idea via first-principles calculations and model analysis of a concrete 2D material example, and show that an electric, continuous, wide-range, and switchable control of valley polarization can be achieved by VLC. Furthermore, we find that systems with VLC can exhibit other interesting physics, such as valley-contrasting linear dichroism and optical selection of the valley and the electric polarization of interlayer excitons. Our finding opens a new direction for valleytronics and 2D materials research.