Selective spectroscopy of tunneling transitions between the Landau levels in vertical double-gate graphene–boron nitride–graphene heterostructures

Resumo

Resonance magnetic tunneling in heterostructures formed by graphene single sheets separated by a hexagonal boron nitride barrier and two gates has been investigated. The design has allowed studying transitions between individual Landau levels of different graphene sheets bounded by a narrow conductivity window with a width controlled by a bias voltage. Three-dimensional plots of the equilibrium tunneling conductivity against both gate voltages reflecting the displacement of resonances between various combinations of the individual Landau levels in the top and bottom sheets have been drawn and identified. The discovered step structure of the current patterns with plateaus and abrupt jumps between them is caused by pinning of chemical potentials to the Landau levels in two graphene sheets. The presence of negative differential conductivity regions in the current–voltage characteristics in the magnetic field with the peak-to-valley current ratio I_p/I_v ~ 2 indicates a high degree of the conservation of an in-plane momentum component at tunneling.