Spatiotemporal carrier dynamics in graphene
Doctoral thesis, 2019

Graphene as an atomically thin material exhibits remarkable optical and
electronic properties that suggest its technological application in novel optoelectronic
devices, such as graphene-based photodetectors and lasers. To understand
the properties of such devices on a microscopic level, we study the
interplay of optical excitation, carrier-carrier, carrier-phonon, and carrierphoton
scattering as well as diffusion processes. We apply a microscopic
model based on the density matrix formalism with spatiotemporal graphene
Bloch equations in its core. This approach provides microscopic access to
the temporally, spectrally and spatially resolved carrier dynamics both in
the presence and absence of an electric field, allowing the study of manyparticle
mechanisms behind photodetection and gain in graphene.
The focus of this thesis lies in modelling optics, dynamics and transport
phenomena on consistent microscopic footing. We predict the possibility to
achieve a stable population inversion in graphene, which is the crucial prerequisite
for using graphene as an active material in a nanolaser. Further,
we provide microscopic insights into the impact of an electric field on the
carrier dynamics revealing the appearance of an efficient dark carrier multiplication
that can even enhance the field-induced current. We also provide a
microscopic foundation for the photoconduction and the bolometric effect as
important mechanisms in a graphene based photodetector. Furthermore, we
provide insights into the spatiotemporal dynamics of optically excited carriers,
which create density and temperature gradients resulting in a diffusion
of carriers. The gained insights can be used to study the thermoelectric effect
and dynamics at interfaces of spatial inhomogeneities.

spatiotemporal dynamics

density matrix formalism

graphene

relaxation dynamics

carrier multiplication

Bloch equations

photoconduction effect

bolometric effect

PJ-salen, Origo, Kemigården 1, Göteborg
Opponent: Professor Doris Reiter, Institute for Solid State Physics, University of Münster, Germany

Author

Roland Jago

Chalmers, Physics, Condensed Matter Theory

Roland Jago, Raül Perea-Causin, Samuel Brem, and Ermin Malic Spatio-temporal dynamics in graphene

Microscopic origin of the bolometric effect in graphene

Physical Review B,; Vol. 99(2019)

Journal article

Microscopic understanding of the photoconduction effect in graphene

Physical Review B,; Vol. 96(2017)p. Article no 085431 -

Journal article

Recombination channels in optically excited graphene

Physica Status Solidi (B): Basic Research,; Vol. 252(2015)p. 2456-2460

Journal article

Graphene as gain medium for broadband lasers

Physical Review B - Condensed Matter and Materials Physics,; Vol. 92(2015)

Journal article

B. Semnani, R. Jago, S. Safavi-Naeini. A. H. Majedi, E. Malic, and P. Tassin Anomalous optical saturation of low-energy Dirac states in graphene and its implication for nonlinear optics

Carrier Dynamics in Graphene: Ultrafast Many-Particle Phenomena

Annalen der Physik,; Vol. 529(2017)

Journal article

Ultrafast momentum imaging of pseudospin-flip excitations in graphene

Physical Review B,; Vol. 96(2017)

Journal article

Experimentally accessible signatures of Auger scattering in graphene

Physical Review B: covering condensed matter and materials physics,; Vol. 94(2016)p. 235430-

Journal article

Graphene as an atomically thin material exhibits remarkable optical and
electronic properties that suggests its technological application in novel op-
toelectronic devices, such as graphene-based lasers and photodetectors. We
show that it is possible to achieve a stable population inversion in graphene,
which is crucial for using graphene as an active material in a nanolaser.
Depending on the experimental conditions there are different mechanisms de-
termining the optical response and the resulting photocurrent. In this thesis
we provide microscopic insights into the photoconduction and the bolometric effect as
important mechanisms in a graphene based photodetector. With our
research we are able to identify microscopic knobs to tune the photocurrent.
Furthermore, we study the interplay of the carrier relaxation and transport
phenomena. We reveal that in the presence of an external electric field an efficient dark carrier multiplication occur, which increses the carrier density,
and even enhance the field-induced current. Moreover, we provide a micro-
scopic description of the spatiotemporal dynamics of optically excited carri-
ers, which create density and temperature gradients resulting in a diffusion
of carriers.

Infrastructure

C3SE (Chalmers Centre for Computational Science and Engineering)

Subject Categories

Atom and Molecular Physics and Optics

Other Physics Topics

Condensed Matter Physics

ISBN

978-91-7905-100-6

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4567

Publisher

Chalmers University of Technology

PJ-salen, Origo, Kemigården 1, Göteborg

Opponent: Professor Doris Reiter, Institute for Solid State Physics, University of Münster, Germany

More information

Latest update

3/28/2019