Abstract
Investigating the structure of quantized plateaus in the Hall conductance of graphene is a powerful way of probing its crystalline and electronic structure and will also help to establish whether graphene can be used as a robust standard of resistance for quantum metrology. We use low-temperature scanning gate microscopy to image the interplateau breakdown of the quantum Hall effect in an exfoliated bilayer graphene flake. Scanning gate images captured during breakdown exhibit intricate patterns where the conductance is strongly affected by the presence of the scanning probe tip. The maximum density and intensity of the tip-induced conductance perturbations occur at half-integer filling factors, midway between consecutive quantum Hall plateau, while the intensity of individual sites shows a strong dependence on tip-voltage. Our results are well-described by a model based on quantum percolation which relates the points of high responsivity to tip-induced scattering in a network of saddle points separating localized states.
Highlights
Quantized plateaus in the Hall conductance of a twodimensional electron system (2DES) develop whenever the Fermi level is in a gap between two Landau levels (LL), making them ideal spectroscopic markers for exploring the sensitivity of LL energy spectra to a wide range of degeneracy-breaking interactions
Our results are well described by a model based on quantum percolation which relates the points of high responsivity to tip-induced scattering between localized Landau levels
Quantum Hall effect (QHE) plateaus occur because electrons in the bulk follow closed and localized paths, while currentcarrying extended states run along the free edges where they are protected from back-scattering and dissipation [5]
Summary
Quantized plateaus in the Hall conductance of a twodimensional electron system (2DES) develop whenever the Fermi level is in a gap between two Landau levels (LL), making them ideal spectroscopic markers for exploring the sensitivity of LL energy spectra to a wide range of degeneracy-breaking interactions. We use low-temperature scanning gate microscopy (SGM) to investigate the breakdown of the quantum Hall regime in an exfoliated bilayer graphene flake.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have