Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
Phys Rev Lett. 2012 Sep 14;109(11):116802. doi: 10.1103/PhysRevLett.109.116802. Epub 2012 Sep 11.
In graphene, as in most metals, electron-electron interactions renormalize the properties of electrons but leave them behaving like noninteracting quasiparticles. Many measurements probe the renormalized properties of electrons right at the Fermi energy. Uniquely for graphene, the accessibility of the electrons at the surface offers the opportunity to use scanned probe techniques to examine the effect of interactions at energies away from the Fermi energy, over a broad range of densities, and on a local scale. Using scanning tunneling spectroscopy, we show that electron interactions leave the graphene energy dispersion linear as a function of excitation energy for energies within ±200 meV of the Fermi energy. However, the measured dispersion velocity depends on density and increases strongly as the density approaches zero near the charge neutrality point, revealing a squeezing of the Dirac cone due to interactions.
在石墨烯中，与大多数金属一样，电子-电子相互作用会使电子的性质发生重整化，但仍保持非相互作用准粒子的行为。许多测量方法都探测了费米能附近电子的重整化性质。独特的是，对于石墨烯来说，表面电子的可及性提供了机会，可以使用扫描探针技术来研究费米能以外的能量范围内、在广泛的密度范围内以及在局部尺度上相互作用的影响。通过扫描隧道谱，我们发现电子相互作用使石墨烯的能谱色散在费米能附近的±200 meV 范围内随激发能呈线性关系。然而，所测量的色散速度取决于密度，并在接近电荷中性点时随着密度的减小而强烈增加，这表明由于相互作用导致了狄拉克锥的压缩。
