22 research outputs found
Weak localisation in bilayer graphene
We have performed the first experimental investigation of quantum
interference corrections to the conductivity of a bilayer graphene structure. A
negative magnetoresistance - a signature of weak localisation - is observed at
different carrier densities, including the electro-neutrality region. It is
very different, however, from the weak localisation in conventional
two-dimensional systems. We show that it is controlled not only by the
dephasing time, but also by different elastic processes that break the
effective time-reversal symmetry and provide invervalley scattering.Comment: 4 pages, 4 figures (to be published in PRL
Quantum Hall activation gaps in bilayer graphene
We have measured the quantum Hall activation gaps in bilayer graphene at
filling factors and in high magnetic fields up to 30 T.
We find that energy levels can be described by a 4-band relativistic hyperbolic
dispersion. The Landau level width is found to contain a field independent
background due to an intrinsic level broadening and a component which increases
linearly with magnetic field.Comment: 4 pages, accepted version (just removed a few typos), will appear as
Fast Track Communication in Solid State Commu
Klein tunneling in graphene: optics with massless electrons
This article provides a pedagogical review on Klein tunneling in graphene,
i.e. the peculiar tunneling properties of two-dimensional massless Dirac
electrons. We consider two simple situations in detail: a massless Dirac
electron incident either on a potential step or on a potential barrier and use
elementary quantum wave mechanics to obtain the transmission probability. We
emphasize the connection to related phenomena in optics, such as the
Snell-Descartes law of refraction, total internal reflection, Fabry-P\'erot
resonances, negative refraction index materials (the so called meta-materials),
etc. We also stress that Klein tunneling is not a genuine quantum tunneling
effect as it does not necessarily involve passing through a classically
forbidden region via evanescent waves. A crucial role in Klein tunneling is
played by the conservation of (sublattice) pseudo-spin, which is discussed in
detail. A major consequence is the absence of backscattering at normal
incidence, of which we give a new shorten proof. The current experimental
status is also thoroughly reviewed. The appendix contains the discussion of a
one-dimensional toy model that clearly illustrates the difference in Klein
tunneling between mono- and bi-layer graphene.Comment: short review article, 18 pages, 14 figures; v3: references added,
several figures slightly modifie
Gate-defined quantum confinement in InSe-based van der Waals heterostructures
Indium selenide, a post-transition metal chalcogenide, is a novel two-dimensional (2D) semiconductor with interesting electronic properties. Its tunable band gap and high electron mobility have already attracted considerable research interest. Here we demonstrate strong quantum confinement and manipulation of single electrons in devices made from few-layer crystals of InSe using electrostatic gating. We report on gate-controlled quantum dots in the Coulomb blockade regime as well as one-dimensional quantization in point contacts, revealing multiple plateaus. The work represents an important milestone in the development of quality devices based on 2D materials and makes InSe a prime candidate for relevant electronic and optoelectronic applications
New solution of the superstring equation of motion
We construct a new solution of the superstring equation of motion and show that this solution satisfies two of Sen's conjectures and does not require "phantom terms." © 2010 MAIK/Nauka
New solution of the superstring equation of motion
We construct a new solution of the superstring equation of motion and show that this solution satisfies two of Sen's conjectures and does not require "phantom terms." © 2010 MAIK/Nauka
On Schnabl solutions of string field equations
We clarify the relationship between Schnabl's solution and pure gauge configurations. Both Schnabl's and pure gauge solutions are obtained by means of an iterative procedure. We show that the pure gauge string field configuration that is used in the construction of a perturbation series for Schnabl's solution diverges on a large subspace of string configurations, but it can be rendered convergent by adding a compensating term. The additional term ensures the fulfillment of the equations of motion in a weak sense. This compensating term coincides with the term necessary for obtaining an action consistent with Sen's first conjecture. © Pleiades Publishing, Ltd 2009
On Schnabl solutions of string field equations
We clarify the relationship between Schnabl's solution and pure gauge configurations. Both Schnabl's and pure gauge solutions are obtained by means of an iterative procedure. We show that the pure gauge string field configuration that is used in the construction of a perturbation series for Schnabl's solution diverges on a large subspace of string configurations, but it can be rendered convergent by adding a compensating term. The additional term ensures the fulfillment of the equations of motion in a weak sense. This compensating term coincides with the term necessary for obtaining an action consistent with Sen's first conjecture. © Pleiades Publishing, Ltd 2009
Field-effect control of tunneling barrier height by exploiting graphene's low density of states
Contains fulltext :
111503.pdf (publisher's version ) (Open Access
Magnetotransport in single-layer graphene in a large parallel magnetic field
Contains fulltext :
161512.pdf (preprint version ) (Open Access