A new class of nanoscale materials

9 July 2015

Dr Wang Yao, a theoretical physicist from The University of Hong Kong, has been working on single-layer two-dimensional semiconductors, a new class of nanoscale materials made in sheets only three atoms thick, in collaboration with experimental physicists at the University of Washington.

Published in Nature Materials in August 2014, the group developed what they believe is the thinnest-possible semiconductor heterojunction. They discovered that two of the monolayer semiconductor materials (group-VIB transition metal dichalcogenides), molybdenum diselenide and tungsten diselenide, can be connected edge-to-edge in an atomically seamless fashion with crystalline perfection. This can be a completely new geometry towards heterostructures, such as quantum dots, which have displayed critical roles in semiconductor technologies.

The researchers’ latest focus is on heterobilayers of these two-dimensional semiconductor materials. There are various 2D materials with distinct appealing properties. For example, graphene with the massless Dirac physics, and monolayer transition metal dichalcogenides with an energy gap in the visible frequency rage and the exotic spin and valley pseudospin physics. “Using these 2D materials as building blocks, and stacking them (like Lego) into heterostructures opens up a new realm to extend and combine the already extraordinary properties of the 2D building blocks. Stacking order and twisting angle between the layers can all be controlled on demand to engineer the device properties. This brings in an extra dimension for exploring the pseudospin-related physics and device applications that have not been available in conventional heterostructures,” said Yao who is leading the current study.

Dr Wang Yao

Another exciting development, published in Nature Nanotechnology in May this year, lies in zero-dimensional nanostructures in the 2D transition metal dichalcogenides. These single photon emitters discovered not only realise single photon source for photonic qubit (the unit for encoding quantum information), but also show the feasibility of using such nanostructures to localise individual electrons so that their spin and valley pseudospin can be exploited as spin-valley qubit for studying quantum spintronics.

Dr Wang Yao is an Associate Professor in the Department of Physics, The University of Hong Kong. He graduated from Peking University and pursued PhD at University of California, San Diego. After postdoctoral training at University of Texas, Austin, he joined HKU as an Assistant Professor at the Physics Department in 2008. His research interests are quantum spintronics, and valley and spin physics in 2D materials and their heterostructures. Yao received a Croucher Innovation Award in 2013.

To view Dr Wang Yao’s Croucher profile, please click here.

For more information about the Croucher Innovation awards, please click here.