Paramagnetic singularities of the orbital magnetism in graphene with a moiré potential

Abstract

The recent detection of the singular diamagnetism of Dirac electrons in a single graphene layer paved a new way of probing 2D quantum materials through the measurement of equilibrium orbital currents which cannot be accessed in usual transport experiments. Among the theoretical predictions is an intriguing orbital paramagnetism at saddle points of the dispersion relation. Here we present magnetisation measurements in graphene monolayers aligned on hexagonal boron nitride (hBN)crystals. Beside the sharp diamagnetic McClure response at the Dirac point, we detect extra diamagnetic singularities at the satellite Dirac points (sDP) of the moiré lattice. Surrounding these diamagnetic satellite peaks, we also observe paramagnetic peaks located at the chemical potential of the saddle points of the Graphene moiré band structure and relate them to the presence of van Hove logarithmic singularities in the density of states. These findings reveal the long ago predicted anomalous paramagnetic orbital response in 2D systems when the Fermi energy is tuned to the vicinity of saddle points.

arXiv commentmain paper 6 pages 5 figures and supplementaray materials 18 pages and 14 figures

References in corpus (22)

• Berry Phase Effects on Electronic Properties
• Hofstadter's butterfly in moire superlattices: A fractal quantum Hall effect
• Massive Dirac fermions and Hofstadter butterfly in a van der Waals heterostructure
• Observation of Van Hove singularities in twisted graphene layers
• Emergence of Superlattice Dirac Points in Graphene on Hexagonal Boron Nitride
• Commensurate-incommensurate transition for graphene on hexagonal boron nitride
• The hot pick-up technique for batch assembly of van der Waals heterostructures
• Twistable electronics with dynamically rotatable heterostructures
• Generic Miniband Structure of Graphene on a Hexagonal Substrate
• Electronic properties of graphene hexagonal boron nitride moiré superlattice
• From dia- to paramagnetic orbital susceptibility of Dirac cones
• Topological Berry phase and semiclassical quantization of cyclotron orbits for two dimensional electrons in coupled band models
• Ballistic miniband conduction in a graphene superlattice
• Geometric orbital susceptibility: quantum metric without Berry curvature
• Imaging Chern mosaic and Berry-curvature magnetism in magic-angle graphene
• Giant oscillations in a triangular network of one-dimensional states in marginally twisted graphene
• Orbital magnetism of coupled bands models
• Classification of Critical Points in Energy Bands Based on Topology, Scaling and Symmetry
• Measurable lattice effects on the charge and magnetic response in graphene
• Detection of graphene's divergent orbital diamagnetism at the Dirac point
• Signatures of van Hove singularities probed by the supercurrent in a graphene - hBN superlattice
• Moiré lattice effects on the orbital magnetic response of twisted bilayer graphene and Condon instability