World first for Australian low-energy electronics research

Researchers from the ARC Centre of Excellence for Future Low-Energy Electronics Technologies (FLEET) at the University of Wollongong and Monash University have found a new phase of matter, the excitonic insulator.

Exitonic insulators have been predicted by scientists since the 1960s but until now have remained a theoretical concept.

The FLEET and Monash University team observed the unique signatures of an excitonic insulating phase in nanoflakes of the chemical element antimony.

The exitonic insulator occurs when electrons and holes in semiconductors and semimetals form electrically neutral pairs, rather than being negatively and positively charged. When electrically neutral, the material may stop conducting electricity, and thus become an excitonic insulator.

Speculation around excitonic insulators has suggested that the material could be used for low-energy electronics that could be used in high-performance computing applications.

Previous attempts to find excitonic insulators have come close, however when examined, the materials showed strong periodical lattice distortion, which would indicate that the charge density wave is driven by electron-phonon coupling, rather than a pure excitonic insulator state.

For the successful observation of these excitonic insulators, the team from FLEET and Monash used scanning tunnelling microscopy and spectroscopy. The discover is a major breakthrough in the field of condensed matter physics, according to Senior Professor Xiaolin Wang, node director of FLEET.

“Our findings of the new excitonic insulator together with the topological insulators and the spin gapless semiconductors are significant for developing new technologies for low energy electronics, which is the main goal of FLEET,” he said.

Other findings by the Institute for Superconducting and Electronic Materials (ISEM), at the University of Wollongong have paved the way for the current discovery. The new class of materials developed at ISEM, spin gapless semiconductors, and topological insulators – a new class of quantum matter – enabled the current research.

“The experimental observation of the new excitonic insulator will boost our research in ISEM on future exploration for new classes of materials and physical properties,” said Wang.