Observing the quantization of zero mass carriers in graphene.
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.
Miller
David L
DL
School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA.
Kubista
Kevin D
KD
Rutter
Gregory M
GM
Ruan
Ming
M
de Heer
Walt A
WA
First
Phillip N
PN
Stroscio
Joseph A
JA