Valleytronics is an emerging field in condensed matter physics and electronics that utilizes the “valley” degree of freedom of electrons in certain materials for storing and processing information.
What Are Valleys?
In the electronic band structure of some crystals (like graphene or transition metal dichalcogenides), electrons can occupy energy extrema—called valleys—at different points in momentum space. These valleys are quantum states that are:
- Energetically equivalent,
- Located at different points in the Brillouin zone,
- And often labeled (e.g., K and K′ in graphene).
How Valleytronics Works:
- Similar to spin in spintronics, the valley index can represent binary information (e.g., valley K = 0, valley K′ = 1).
- External stimuli like electric fields, magnetic fields, circularly polarized light, or strain can control valley populations.
- Devices can be designed to selectively manipulate and detect electrons based on their valley state.
Applications and Significance:
- Low-power electronics: Since valley states can be controlled with less energy than traditional charge-based electronics.
- Quantum computing: Valley states may act as qubits.
- 2D materials: It’s particularly promising in atomically thin materials like MoS₂, WS₂, and graphene.
Valleytronics is still a developing field, but it offers a novel route to next-generation information technologies by using momentum-space states rather than charge or spin alone.