Seminar Announcement
“Investigations of the electronic and
vibrational properties of trilayer graphene by
optical spectroscopy”
Chun Hung Lui
Department of Physics, Columbia University
Hosted by: Jiwoong Park
Thursday, November 10, 2011
458 S.T. Olin Lab
2:00 pm
Graphene-based materials have stimulated intense interest because of their remarkable
electronic properties and potential for novel applications. With the impressive progress
in research on graphene mono- and bilayers, recent attention has also turned to
graphene’s trilayer counterpart. In trilayer graphene, the crystallographic stacking of the
individual graphene sheets provides an additional degree of freedom. Trilayer graphene
can exist in two stable crystallographic configurations: ABA and ABC stacking order. The
distinct lattice symmetries associated with these two types of trilayer allotropes have
been predicted to strongly influence the material’s physical properties. Here we have
carried out using infrared and Raman spectroscopy systematic experimental
investigations on the electronic and vibrational properties of graphene trilayers with ABA
and ABC stacking order under an electrical gate. Our results show strong contrast in the
gated behaviors of these two types of trilayers. We find that the electronic band structure,
electrically tunable band gap, electron-phonon interaction and infrared phonon
absorption of graphene trilayers are critically dependent on the stacking sequence. In
particular, we observe the induction of a large tunable band gap in ABC trilayers with the
application of a strong perpendicular electric field, while such a band gap is not
observable in ABA trilayers under the same electric field. In addition, the infrared phonon
absorption in ABC trilayers shows much larger gate dependence than in ABA trilayers.
We analyze these results by considering the implications of the different crystal structure
and interlayer coupling in ABA- and ABC-stacked trilayers.