Graphene knock-offs probe ultrafast electronics
In May 22nd Nature News:
“If imitation is the sincerest form of flattery, then graphene is basking in admiration. Several labs are recreating the six-fold geometry of the carbon-based material with a range of building blocks, hoping to match — if not surpass — graphene’s fascinating properties.
The approaches span a range of length scales, from nanometres to millimetres (see ‘Lattice lookalikes’), and take advantage of a variety of construction techniques, including potassium atoms trapped by laser beams, hexagons etched on a gallium arsenide surface and microwaves pumped into a honeycomb arrangement of ceramic cylinders. The research is mostly motivated by curiosity, and few think that any of the ‘artificial graphenes’ will be used in applications. But the new materials show that hexagonal patterns are worth investigating. ‘It’s clear the physics in electrons in graphene is very attractive,´ says Eros Mariani, a theoretical physicist at the University of Exeter, UK.
´To mimic graphene sounds pretty boring scientifically and a waste of time and resources,’ says Antonio Castro Neto, director of the Graphene Research Centre at the National University of Singapore. ‘The objective of creating these artificial graphene-like lattices is to produce new systems that have properties that graphene does not have.’
For example, he has predicted that etching a honeycomb structure onto a semiconductor such as gallium arsenide could turn it into a topological insulator — a much-sought material that insulates in its interior but conducts superbly well on its surface, where exotic particles called Majorana fermions might emerge. These particles, which have been tentatively observed in one-dimensional nanowires, have a unique ability to encode quantum information by swapping locations with each other (see Nature 483, 132; 2012). Hexagonal gallium arsenide lattices have been made on large scales, but Castro Neto says that current methods of nanolithography should enable researchers to etch them at scales of 20 nanometres or less, fine enough to see the Majoranas.
Although it will be a long time before artificial graphenes can be used in quantum computing, Castro Neto doesn’t rule out a pay-off for them. ‘I am always surprised that people find applications for things I thought would never be useful,’ he says.”