Electrons within solid materials are restricted to specific energy levels, known as “bands.” The space between these bands, the forbidden energies, are known as “band gaps.” Both of them together constitute the “band structure” of the material, which is a unique characteristic of each specific material.
When physicists plot the band structure, they usually see that the resulting curves resemble mountains and valleys. In fact, the technical term for a local energy maximum or minimum in the bands is called a “valley,” and the field that studies and exploits how electrons in the material switch from one valley to the other is coined “valleytronics.”
In standard semiconductor electronics, the electric charge of the electrons is the most used property exploited to encode and manipulate information. But these particles have other properties that could also be used for the same purpose, such as the valley they are in. In the past decade, the main aim of valleytronics has been to reach the control of the valley population (also known as valley polarization) in materials. Such an achievement could be used to create classical and quantum gates and bits, something that could really drive the development of computing and quantum information processing.
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