A new topological insulator

For the first time, physicists have constructed a unique topological insulator in which optical and electronic excitations hybridize and flow together. They report their discovery in Nature.

Topological insulators are materials with very particular properties. They only conduct electricity or light particles on their surface or edges, not on the inside. This unusual feature could provide technical innovations, and topological insulators have been the subject of intensive global research for several years.

Physicists from the Julius Maximilians Universität Würzburg (JMU) in Bavaria, Germany, accompanied by colleagues from the Haifa Technion (Israel) and the Nanyang Technological University in Singapore, announced their discovery in the newspaper Nature. The team built the first "exciton-polariton topological isolator", a topological isolator operating simultaneously with light and electronic excitations.

Professor Sven Höfling, who heads the JMU Chair in Applied Physics, explains that these topological insulators have a dual advantage: "They could be used for both switching electronic systems and laser applications." The topological insulators previously developed are based on electrons or photons alone.

Dr. Sebastian Klembt, group leader at Höfling, played a leading role in the project. It gives more details: "The new topological insulator was built on a microchip and consists of a semiconductor compound based on gallium arsenide.It has a honeycomb structure and consists of many small pillars of two micrometers (two diameters. "

The direction of propagation can be controlled

When you excite this microstructure with a laser light, particles of light material form inside, exclusively on the edges. The particles then move along the edges and corners with a relatively small loss. "A magnetic field allows us to control and reverse the direction of particle propagation," says Klembt.

This is a sophisticated system that works in a microchip in dimensions suitable for the application and in which the light can be controlled. This is usually difficult to achieve: the particles of pure light have no electric charge and therefore can not be easily controlled by electric or magnetic fields. The new topological insulator is able to do this by "sending the light from the corner", so to speak.

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More information:
S. Klembt et al., Exciton-Polariton topology insulator, Nature (2018). DOI: 10.1038 / s41586-018-0601-5