Physicists discover entirely new quantum states when graphene meets itself. In other words, one graphene layer is good, but two are out of this world.
“The super-thin ‘wonder material’ graphene has been shaking up science for years with its amazing properties, but things get really interesting when you stack this 2D nano-material up against itself.
In new experiments, physicists in the US have found that when graphene is assembled in a double-layer vertical stack – with two adjacent sheets of the material that are almost touching – the proximity produces quantum states that haven’t been observed before.
These newly measured states, resulting from complex interactions of electrons between the two graphene layers, are examples of what’s called the fractional quantum Hall effect – and it’s just the latest example of how physical science gets weird when materials effectively only occupy two dimensions.
“The findings show that stacking 2D materials together in close proximity generates entirely new physics,” says physicist Jia Li from Brown University.
“In terms of materials engineering, this work shows that these layered systems could be viable in creating new types of electronic devices that take advantage of these new quantum Hall states.”
The roots of the new discovery trace back some 140 years, to when scientists first discovered what became known as the Hall effect: the way that voltage can be deflected by the presence of a magnetic field.
This so-called Hall voltage runs in the transverse direction as a result of the Hall effect, which is amplified if the magnetic field being applied becomes stronger.”
In the new work, the two graphene layers were separated by a thin layer of hexagonal boron nitride, which was inserted to act as an insulating barrier. The device was also surrounded by hexagonal boron nitride, and connected to graphite electrodes.”
The findings are reported in Nature Physics.
Source: Science Alert by Peter Dockrill