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Chiral interface states in graphene pn-junctions in magnetic field

Tuesday, September 12, 2017 - 12:00
Donostia International Physics Center
Alessando de Martino (City Univeristy of London)
Source Name: 

In the last few years, the
ballistic transport regime has become routinely accessible in high-quality
graphene devices. This development has generated a renewed interest in the
transport properties of graphene pn junctions. In this talk, I will present a
theoretical study of the interface states which form near pn junctions in
a graphene monolayer subject to a perpendicular magnetic field. I will discuss
the exact and essentially analytical solution of the quantum-mechanical
eigenproblem for both a straight and a disc-shaped junction. In both cases, the
spectrum consists of localized Landau-like and unidirectional propagating interface
states. The semiclassical limit of these states corresponds to trajectories
propagating along the pn interface by a combined skipping-snaking motion. For a
straight junction, the group velocity of the chiral mode originating from the
zeroth Landau level interpolates as function of the potential step height
between the classical drift velocity in a crossed electromagnetic field and the
semiclassical value expected for a purely snaking motion. Away from the Dirac
point, the chiral interface states resemble the conventional skipping orbits
found also in the corresponding Schrödinger problem. In the case of a circular
geometry, the chiral interface states are predicted to carry sizeable
circulating currents. 

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