2013 Innovation Award: Dr Wang Yao
Yao is currently investigating how internal degrees of freedom of the electron such as spin, layer and valley can be applied to the development of new concept electronics and how their quantum mechanical behaviour can be utilised for information processing.
Currently, computers use the binary codes 0 and 1 that are charge configurations of high and low voltage representing information. Instead of using the electron charge state to encode information, internal degrees of freedom like spin could be used instead. Another internal degree of freedom is in a crystal where one two-dimensional layer stacks upon another, the status of an electron being in the upper layer is equivalent to 0 while the lower layer is equivalent to 1 of the binary code. This is called the layer pseudo-spin, which may be used for encoding information.
According to the band theory of solids, there is another degree of freedom called the valley pseudo-spin – the name given to minima of energy bands in momentum space. Electron energy can be seen as a function of momentum or velocity and those energy dispersions has some degenerate minima. All these degrees of freedom, spin, layer and valley, can be used to encode information and the control of these degrees of freedom enables information processing. Utilising these degrees of freedom especially with their quantum mechanical properties may bring renewed functionality to electronic devices. Yao’s current focus is to explore these degrees of freedoms in new materials like graphene and two-dimensional transition metal dichalcogenides.
Yao and his co-workers predicted the physics associated with valley pseudo-spin, previously thought to be unusable as there was no control over the dynamics of this degree of freedom. They anticipated that when breaks in inversion symmetry of the system occur, the valley pseudo-spin acquires distinguishable physical quantities that allow differentiation of valley states. The control of the valley pseudo-spin therefore becomes possible so it becomes a qualified carrier of information. Yao’s research contributes to valley-tronics by breaking the inversion symmetry in the system thereby acquiring the valley Hall effect and valley optical selection rule, which allow control of the valley. This field, initiated by Yao and his co-workers is called valley-optoelectronics.
Although Yao’s research is still at the elementary conceptual stage, these aspects can potentially change the way computation or information processing is done. In time, this will hopefully lead to the development of devices with better functionality, that is, faster speed and larger computational capacity or even a quantum computer.
Wang Yao received his B.S. in Physics (2001) from Peking University and a PhD (2006) from University of California, San Diego. He was a postdoctoral fellow at University of Texas, Austin (2006-2008) prior to his appointment as Assistant Professor at the Physics Department, University of Hong Kong. His research has been published in Nature, Nature Communications, Physical Review Letters, Nature Nanotechnology and Nature Physics.
To view Wang Yao's personal Croucher profile, please click here.