6/12/2023 0 Comments Low energy graphene dispersioSo far, transport experiments in graphene have shown results in agreement with the presence of Dirac fermions 1, 2. The Dirac fermions are proposed to be responsible for various anomalous phenomena observed in these systems 1, 2, 3, 8. The low-energy excitations in this case are Dirac fermions, which have zero effective mass and a vanishing density of states at the Dirac point. For some special systems, for example, graphene/graphite, where the dispersion is expected to be linear near the Fermi energy, E F, and only touch E F at one point (Dirac point), the physics is described by the relativistic Dirac equation with the speed of light replaced by the Fermi velocity v F. Thus, graphite presents a system in which massless Dirac fermions, quasiparticles with finite effective mass and defect states all contribute to the low-energy electronic dynamics.įor most condensed-matter systems, the physics is formulated in terms of the non-relativistic Schrödinger equation, and the low-energy excitations are quasiparticles with finite effective mass. In addition, we also report a large electron pocket that we attribute to defect-induced localized states. Here, we report the first direct observation of relativistic Dirac fermions with linear dispersion near the Brillouin zone (BZ) corner H, which coexist with quasiparticles that have a parabolic dispersion near another BZ corner K. Despite their proposed key role in those systems, direct experimental evidence of Dirac fermions has been limited. 5) and the exotic pseudogap phase of high-temperature superconductors 6, 7. Originating from relativistic quantum field theory, Dirac fermions have been invoked recently to explain various peculiar phenomena in condensed-matter physics, including the novel quantum Hall effect in graphene 1, 2, the magnetic-field-driven metal–insulator-like transition in graphite 3, 4, superfluidity in 3He (ref.
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