Fudan researchers achieve scientific breakthrough

Researchers from Fudan University in Shanghai and Cornell University in the United States have found evidence of a new type of quantum Hall effect existent in nanostructures of three-dimensional topological semimetal.

The research, published online in Nature on Monday, represents a breakthrough in the research of the quantum Hall effect, which, discovered decades ago, remains one of the most studied phenomena in condensed matter physics. Studies of the quantum Hall effect is relevant to research areas such as topological phases, strong electron correlations and quantum computing.

Before the recent discovery, the quantum Hall effect was observed and investigated only in two-dimensional electron systems when subjected to low temperatures and strong magnetic fields.

While there has been intense interest in exploring the quantum Hall effect in higher dimensions, conditions for relevant observation are highly demanding. It took the research team three years to develop high-quality nanostructures of topological semimetals for the experiment, said Xiu Faxian, a professor in physics from Fudan University who is the corresponding author of the research paper in Nature.

Xiu's two doctoral students Zhang Cheng and Yuan Xiang, along with Zhang Yi, a Fudan alumnus and a post-doctor at Cornell University, are the co-first authors of the paper.

The team first discovered the existence of the quantum effect in three-dimensional nanostructures of semimetal last year, which was also reported in Nature Communications in November 2017. The discovery was later confirmed by another two similar research projects in Japan and the United States.

Over the past year, Xiu and his students have fine tuned their experiment with extricate designs that allow a clear observation of the underlying physics of the quantum Hall effect in three-dimensional structures.

Xiu said the discovery is only a start in the exploration of quantum Hall physics in three-dimensional materials.

"Much remains unknown and we're keen to explore further," Xiu said.

Xiu added that the team and the rest of the scientific community can tap into one legacy of their recent success.

"We have proved that nanostructures of topological semimetals provide a way of exploring quantum Hall physics in three-dimensional materials with enhanced tunability," Xiu said.