Laboratoire National des Champs Magnétiques Pulsés CNRS – INSA

SCIENTIFIC ACTIVITIES
Spectroscopy of nano- and meso-systems
Contributors: M. Byszewski, S. Moreau, B. Pietka, O. Fedorych, C. Koerdt, K. Kowalik, M. Orlita,
P. Plochocka, M.L. Sadowski, F.J. Teran, C. Faugeras, G. Martinez, D.K. Maude, M. Potemski
Collaborators: A. Babinski (University of Warsaw, Poland), I. Bar-Joseph (Weizmann Institute, Israel), A-
L. Barra (LNCMI-Grenoble), M. Bayer (University of Dortmund, Germany), C. Berger (Institut Néel,
Grenoble, France), L. Bryja (Technical University of Wroclaw, Poland), Yu. Bychkov (Landau Institute,
Chernogolovka, Russia), J-N. Fuchs, M. Goerbig (LPS, Orsay), Y. Guldner (LPA-ENS, Paris), P. Hawrylak
(IMS-NRC, Canada), W.A. de Heer (Georgia Tech at Atlanta, USA), Y. Hirayama (Tohoku University,
Japan), R.J. Nicholas (Oxford University, U.K.), A. Pinczuk (Columbia University, USA), S. Raymond (IMS-
NRC, Canada), M. Skolnick (University of Sheffield, U.K.), S.A. Studenikin (IMS-NRC, Canada),
Z.R. Wasilewski (IMS-NRC, Canada), A. Wysmolek (University of Warsaw, Poland)
The physics of low dimensional systems (semiconductor structures and two-dimensional allotropes
of carbon) in combination with spectroscopic methods and magnetic field techniques is the central theme of
our research activity. Low dimensional systems had and continue to have a great impact on solid state
physics and on technology. They are exceptionally suitable for studying the fundamental quantum
mechanical phenomena and allow producing more and more efficient electronic devices. Applications of
magnetic fields play an important role in the investigations of low-dimensional systems. This is best
demonstrated by the discoveries of quantum Hall effects. These effects, representative for the physics of a
two-dimensional electron gas in semiconductor heterostructures, are the consequence of the unique energy
structure of two-dimensional systems in a magnetic field, which represent highly, eB/h-degenerate discrete
(Landau) levels. The energy levels of zero-dimensional systems, such as semiconductor quantum dots, are
already discrete in the absence of the magnetic field. Nevertheless, the application of this field introduces a
characteristic (magnetic) length, which can be comparable with the size of the dot (extension of the
electronic wave-function) what leads to essential modification of electronic orbitals and in consequence to
important changes in the energy diagrams of these systems. Magneto-spectroscopy and/or electronic
properties of low dimensional systems in magnetic field and under electro-magnetic wave excitation are the
representative axis of our research activity.
The relevant part of our recent activity has been focused on studies of electronic properties of
graphene (single sheet of graphite) and its derivatives. Our contributions to this emergent research area
concerns magneto-optical studies which, in contrast to more common, electric transport methods, provide
almost direct information on band structure of solids. Our group was the first to demonstrate the “Dirac like”
electronic dispersion relations of graphene-based structures using magneto-spectroscopy methods [Sad06].
Importantly, our work has shown that the Dirac-like electronic spectrum is not only characteristic of a single
graphene layer but persists in structures of multilayer graphene on C-terminated surface of silicon carbide
(C-SiC), which were used in our experiments. This initially surprising conclusion has been later confirmed in
our Raman scattering experiments [Fau08] and is today a well established, important fact.
The appearance of the Dirac-like electronic states in graphene structures on C-phase of SiC in
combination with high, room temperature electron mobilities which we have reported in these
systems [Orl08b] is important from the viewpoint of possible applications in electronics. Graphene on C-SiC
may be also the material of choice to further explore the fundamental physics of Dirac fermions in solid state
labs. Fermions in graphene are obviously not “real fermions” but only quasiparticles characteristic of band
states in solids. Nevertheless, our more recent works [Plo08] show that Dirac-like states in graphene extend
over a wide energy range (only small nonlinear effects occur, but far away from the zero Dirac point). Our
magneto-optical experiments also show that the majority of the C-SiC graphene layers are practically neutral
and that the electronic states from the immediate vicinity of the zero-Dirac point, which physics is perhaps
the most spectacular, can be investigated in these structures [Orl08b].
A few of our recent works [Orl08a, Orl09, Sch09] have aimed at reviewing the electronic properties
of graphite. This material is far more complex than graphene, but electronic states of graphite also involve
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