Quantum Tech

Quantum electronics breakthrough sparks new debates

23rd April 2024
Harry Fowle

An international research team, led by the University of Göttingen, has experimentally shown that electrons in double-layer graphene, found naturally, behave as if they are massless, akin to the manner in which light travels, opening possibilities for quantum electronics. 

Moreover, it has been demonstrated that the flow of these electrons can be turned on and off, suggesting the possibility of developing extremely small, energy-efficient transistors, comparable to a nanoscale light switch. Collaborating on this research were the Massachusetts Institute of Technology (MIT) in the USA and the National Institute for Materials Science (NIMS) in Japan, with the findings published in Nature Communications.

Graphene, discovered in 2004, is a single layer of carbon atoms notable for its exceptional electrical conductivity. This property is due to the high and consistent velocity at which electrons move through the material, making graphene a prime candidate for significantly faster and more energy-efficient transistors. However, the challenge has been to manage graphene in such a way that it can toggle between highly conductive and highly insulating states—a critical requirement for transistor functionality. Typically, graphene lacks an insulating state, which has restricted its application in transistor technology.

The team from Göttingen University has discovered that double-layer graphene, which occurs naturally, combines these necessary properties: it supports the ultra-fast movement of massless electrons and can achieve an insulating state. This dual functionality was achieved by applying an electric field perpendicularly to the layers, switching the double-layer graphene to an insulating state. Although this phenomenon was predicted as early as 2009, it required significantly improved sample quality, as provided by NIMS, and a deep collaborative effort on the theoretical aspects with MIT, to be experimentally confirmed. Although the experiments required cryogenic temperatures, around -273°C, they underscore the potential of bilayer graphene in creating highly efficient transistors.

"We were already aware of the theory. However, now we have carried out experiments which actually show the light-like dispersion of electrons in bilayer graphene. It was a very exciting moment for the entire team," says Professor Thomas Weitz, at Göttingen University’s Faculty of Physics. Dr Anna Seiler, Postdoctoral Researcher and First Author also at Göttingen University, adds: “Our work is very much a first step but a crucial one. The next step for researchers will be to see if bilayer graphene really can improve transistors or to investigate the potential of this effect in other areas of technology.”

Original publication: Anna M. Seiler et al. “Probing the tunable multi-cone band structure in Bernal bilayer graphene”, Nature Communications 2024. Doi: 10.1038/s41467-024-47342-0 and https://rdcu.be/dErrl.

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