Source: School of Physics
Written by: School of Physics
Edited by: Wang Dongmei

In 2016, Nobel physics prize was awarded to David Thouless, Michael Kosterlitz and Duncan Haldane for their contributions in topological phase transitions and topological phases of matter. In the past few years, the application of topology is creating new opportunities in photonics. Some quantized electromagnetic behaviors at the boundary of nontrivial topological photonic systems imply great potential applications in unidirectional transport, photonic Weyl point, optical delay line, and topological quantum computer. Generally speaking, the quantized electromagnetic behaviors are believed to only exist in topologically nontrivial systems. It is an open question that whether one can achieve quantized electromagnetic behaviors in trivial systems.

Scientists with the School of Physics and State Key Laboratory of Optoelectronic Materials and Technologies (OEMT) in Sun Yat-sen University (SYSU) have answered this question in the affirmative. “The key problem is how to realize another kind of interaction in a trivial photonic system.” says Jianwen Dong who led this study. “We exploit another intrinsic degree of freedom, so-called valley, to solve the issue.” Followed such mechanism, they have achieved valley-dependent spin-split bands, leading to the photonic spin-momentum locking transport, i.e. photonic valley Hall effect. Unidirectional spin flow can also be designed in such topologically trivial photonic system.


Dong, who is elected in NSFC Excellent Young Scientists, is the first author of a paper describing this physics research in the journal Nature Materials. The paper is titled “Valley photonic crystals for control of spin and topology” and see detailed results through the link of http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat4807.html. This work is cooperated with a US team of Professor Xiang Zhang from University of California, Berkeley.

"The independent control of valley and topology can be achieved in one single valley photonic crystal, which is a long dream in condense matter field” says Xiaodong Chen, co-first author of the Nat. Mater. paper and the associate research fellow of Professor Dong’s group. Valley photonic crystals not only offer a route towards the observation of non-trivial states, but also open the way for device applications in integrated photonics and information processing using spin-dependent transportation.

This research was supported by the grants of NSFC, OEMT, and SYSU.

Additional Information
Jianwen Dong can be reached for more about the research and comment at dongjwen@mail.sysu.edu.cn and http://dgroup.sysu.edu.cn.