In recent years, graphene, a two dimensional sheet of carbons atoms, has received a lot of attention from condensed matter experimentalists as well as theorists. Due to its unique characteristics it is now possible to study, using graphene based experiments, phenomenon that existed only as theoretical concepts. .
In presence of the magnetic field, its unique band structure gives rise to anomalous quantum Hall effect, unique to monolayer. We have explored the limit of breakdown of the quantum Hall state in graphene with electric field and have tried to understand the mechanism behind it.
Suspension of the graphene flake above the substrate leads to high mobility ( >200,000 cm 2/V sec) of charge carriers low temperatures). We are also looking at the electron transport in these ultra clean samples.
Being the thinnest and stiffest material (Young’s modulus ~ 1TPa) in two dimensions, graphene is also an ideal candidate for its application to nanoelectromechanical systems (NEMS). We have studied the suspended graphene devices in the form of NEMS resonators from room temperature down to 5K. Typical resonance frequency of these resonators in micron size geometry is of the order of tens of MHz. Suspended geometry in these graphene devices allows us to measure the thermal expansion coefficient of the graphene and the tunability of the resonance frequency with external knobs like gate voltages at all temperatures.