Seminários

Seminário de Física da Matéria Condensada

Nesta quinta-feira (11/04) às 11h na sala 429 (torre nova) teremos o
seminário do palestrante Eliel Silva. São todos muito bem vindos!
Segue abaixo o título e resumo:

Palestrante: Eliel Silva (UFF)

Titulo: Intralayer and interlayer electron-phonon interactions in
twisted graphene heterostructures

Resumo: Two-dimensional materials have attracted much attention in
many fields of physics due to their electrical, magnetic, optical and
mechanical properties. The possibility of combine those properties
producing ultrathin devices is outstanding. Stacking those materials
to create van der Waals heterostructures originates new phenomena that
depend not only the materials stacking order, but also the relative
crystalline orientation among them. The understanding of interactions
between electrons and phonons in ultrathin heterostructures is crucial
for the engineering of novel two-dimensional devices. Electron-phonon
(el-ph) interactions in layered materials can occur involving
electrons in the same layer or different layers. We report on the
possibility of distinguishing intralayer and interlayer el-ph
interactions in samples of twisted bilayer graphene and of probing the
intralayer process in graphene/h-BN by using Raman spectroscopy. Our
samples were produced in two different ways. The twisted bilayer
graphene samples were produced via a chemical vapor deposition
technique and then transferred to 300 nm SiO2/Si substrate. The
graphene/h-BN heterostructures were fabricated via discrete
transference method. We acquired Raman spectra in 19 laser lines going
from infrared up to ultraviolet in a large group of twisted bilayer
graphene samples with different stacking angles. Our results show that
the intralayer process, the el-ph scattering occurs in a single
graphene layer and the other layer (graphene or h-BN) imposes a
periodic potential that backscatters the excited electron, whereas for
the interlayer process the el-ph scattering occurs between states in
the Dirac cones of adjacent graphene layers. Our methodology of using
Raman spectroscopy to probe different types of el-ph interactions can
be extended to study any graphene-based heterostructure.