Mercredi 16 mai 2012 à 11h15
Salle 234, Ecole de Physique

Crossover from Coulomb blockade to quantum-Hall effect in suspended graphene nanoribbon

Dong-Keun Ki, University of Geneva

We present the magneto-transport measurements on high-quality suspended graphene nanoribbons formed when current annealing wide suspended graphene layers. Our data show that the devices obtained in this way have much higher quality as compared to nanoribbons on substrates, exhibiting clear quantum-Hall conductance quantization at magnetic fields as low as $sim 2 T$. The quantum Hall state evolves from a state (at $B=0T$) characterized by a transport gap due to disorder induced Coulomb blockade. In suspended nano-ribbons, we also succeeded in observing a magnetic field induced opening of the energy gap around the charge neutrality originating from electron-electron interaction. Since this gap is suppressed by disorder, its observation provides one more indication of the high quality of suspended graphene nanoribbons. These results demonstrate the potential of suspended nanoribbons for the investigation of Dirac electrons in confined geometries.