1 research outputs found
Non-Drude THz conductivity of graphene due to structural distortions
The remarkable electrical, optical and mechanical properties of graphene make
it a desirable material for electronics, optoelectronics and quantum
applications. A fundamental understanding of the electrical conductivity of
graphene across a wide frequency range is required for the development of such
technologies. In this study, we use terahertz (THz) time-domain spectroscopy to
measure the complex dynamic conductivity of electrostatically gated graphene,
in a broad 0.1 - 7 THz frequency range. The conductivity of doped
graphene follows the conventional Drude model, and is predominantly governed by
intraband processes. In contrast, undoped charge-neutral graphene exhibits a
THz conductivity that significantly deviates from Drude-type models. Via
quantum kinetic equations and density matrix theory, we show that this
discrepancy can be explained by additional interband processes, that can be
exacerbated by electron backscattering. We propose a mechanism where such
backscattering -- which involves flipping of the electron pseudo-spin -- is
mediated by the substantial vector scattering potentials that are associated
with structural deformations of graphene. Our findings highlight the
significant impact that structural distortions and resulting electrostatic
vector scattering potentials can have on the THz conductivity of charge-neutral
graphene. Our results emphasise the importance of the planar morphology of
graphene for its broadband THz electronic response.Comment: 74 pages, 21 figure