Observing the Quantization of Zero Mass Carriers in Graphene
David L. Miller,1,*
Kevin D. Kubista,1,*
Gregory M. Rutter,2
Ming Ruan,1
Walt A. de Heer,1
Phillip N. First,1,
Joseph A. Stroscio2,
Application of a magnetic field to conductors causes the charge
carriers to circulate in cyclotron orbits with quantized energies
called Landau levels (LLs). These are equally spaced in normal
metals and two-dimensional electron gases. In graphene, however,
the charge carrier velocity is independent of their energy (like
massless photons). Consequently, the LL energies are not equally
spaced and include a characteristic zero-energy state (the
n = 0 LL). With the use of scanning tunneling spectroscopy of
graphene grown on silicon carbide, we directly observed the
discrete, non-equally–spaced energy-level spectrum of
LLs, including the hallmark zero-energy state of graphene. We
also detected characteristic magneto-oscillations in the tunneling
conductance and mapped the electrostatic potential of graphene
by measuring spatial variations in the energy of the
n = 0 LL.
2 Center for Nanoscale Science and Technology, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, USA.
* These authors contributed equally to this work.
To whom correspondence should be addressed: first{at}physics.gatech.edu (P.N.F.); joseph.stroscio{at}nist.gov (J.A.S.)
