Topological phenomena, like the protected edge mode in which waves can travel around large imperfections without back-reflection, envision enticing applications. Although initially emerging from the study of the quantum Hall effect, topological phases are universal in various fields, including photonics, mechanics, and phononics. In this talk, I will discuss my topological phase engineering work. I will show some results in CVD few-layer graphene, particularly in engineering AB/BA domain walls where quantum valley Hall edge modes are afforded. Then I will present some results of topological phononics in piezoactive materials, which are essential for applications in communications, quantum information science, sensing, etc. First, I will demonstrate valley Hall phases in piezoelectric AlN at GHz. Second, a theoretical framework for studying topological phases in piezoelectric and piezomagnetic materials will be discussed. Here I will reveal that an unexpected factor, the general duality relation, plays a crucial role in engineering symmetry breaking and topological phases.
 

Qicheng Zhang is on a transition from a Postdoctoral Researcher in the Department of Physics and Astronomy at the University of Pennsylvania to an Assistant Professor in the School of Engineering at Westlake University. He received his bachelor’s degree in Polymer Materials and Engineering from Zhejiang University in 2012. In 2016, he earned his Ph.D. in Chemical and Biomolecular Engineering from the Hong Kong University of Science and Technology, where he studied the properties of van der Waals materials. In 2018, he began his postdoc journey at the University of Pennsylvania, where he worked on developing rapid and scalable handheld devices of carbon nanotube gas sensors for disease screening, engineering van der Waals materials for exploration of their topological physics, and, more recently, integrated topological phononic circuitry.

Please contact phweb@ust.hk should you have questions about the talk.