Stopping the unstoppable with atomic bricks
Graphene's unique 2D structure means that electrons travel through it differently to most other materials. One consequence of this unique transport is that applying a voltage to them doesn't stop the electrons like it does in most other materials. This is a problem because to make useful applications out of graphene and its unique electrons like quantum computers, it is necessary to be able to stop and control graphene electrons.
An interdisciplinary team of scientists from the Universidad Autonoma de Madrid (Spain), Universit茅 Grenoble Alpes (France), International Iberian Nanotechnology Laboratory (Portugal) and Aalto University has managed to solve this long-standing problem. They combined experimental researchers including Eva Cort茅s del R铆o, Pierre Mallet, H茅ctor Gonz谩lez鈥怘errero, Jos茅 Mar铆a G贸mez鈥怰odr铆guez, Jean鈥怸ves Veuillen and Iv谩n Brihuega with theorists, including Joaqu铆n Fern谩ndez-Rossier and Jose Lado, assistant Professor in the department of Applied Physics at Aalto.
The experimental team used atomic bricks to build walls capable of stopping the graphene electrons. This was achieved by creating atomic walls that confined the electrons, leading to structures whose spectrum was then compared with theoretical predictions, demonstrating that electrons were confined. In particular, it was obtained that the engineered structures gave rise to nearly perfect confinement of electrons, as demonstrated from the emergence of sharp quantum well resonances with a remarkably long lifetime.
The work, published this week in , demonstrates that impenetrable walls for graphene electrons can be created by collective manipulation of a large number of hydrogen atoms. In the experiments, a scanning tunnelling microscope was used to construct artificial walls with sub nanometric precision. This led to graphene nanostructures of arbitrarily complex shapes, with dimensions ranging from two nanometres to one micron.
Importantly, the developed method is non-destructive, allowing to erase and rebuild the nanostructures at will, providing an unprecedented degree of control to create artificial graphene devices. The experiments demonstrate that the engineered nanostructures are capable of perfectly confining the graphene electrons in these artificially designed structures, overcoming the critical challenge imposed by Klein tunnelling. Ultimately, this opens up a plethora of exciting new possibilities, as the created nanostructures realize graphene quantum dots that can be selectively coupled, opening ground-breaking possibilities for artificially designed quantum matter.
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