295 research outputs found
Edge states, spin transport and impurity induced local density of states in spin-orbit coupled graphene
We study graphene which has both spin-orbit coupling (SOC), taken to be of
the Kane-Mele form, and a Zeeman field induced due to proximity to a
ferromagnetic material. We show that a zigzag interface of graphene having SOC
with its pristine counterpart hosts robust chiral edge modes in spite of the
gapless nature of the pristine graphene; such modes do not occur for armchair
interfaces. Next we study the change in the local density of states (LDOS) due
to the presence of an impurity in graphene with SOC and Zeeman field, and
demonstrate that the Fourier transform of the LDOS close to the Dirac points
can act as a measure of the strength of the spin-orbit coupling; in addition,
for a specific distribution of impurity atoms, the LDOS is controlled by a
destructive interference effect of graphene electrons which is a direct
consequence of their Dirac nature. Finally, we study transport across junctions
which separates spin-orbit coupled graphene with Kane-Mele and Rashba terms
from pristine graphene both in the presence and absence of a Zeeman field. We
demonstrate that such junctions are generally spin active, namely, they can
rotate the spin so that an incident electron which is spin polarized along some
direction has a finite probability of being transmitted with the opposite spin.
This leads to a finite, electrically controllable, spin current in such
graphene junctions. We discuss possible experiments which can probe our
theoretical predictions.Comment: 21 pages, 19 figures; added some discussion and references; this is
the final published versio
Designing bound states in a band as a model for a quantum network
We provide a model of a one dimensional quantum network, in the framework of
a lattice using Von Neumann and Wigner's idea of bound states in a continuum.
The localized states acting as qubits are created by a controlled deformation
of a periodic potential. These wave functions lie at the band edges and are
defects in a lattice. We propose that these defect states, with atoms trapped
in them, can be realized in an optical lattice and can act as a model for a
quantum network.Comment: 8 pages, 10 figure
Growth mechanism of nanocrystals in solution: ZnO, a case study
We investigate the mechanism of growth of nanocrystals from solution using
the case of ZnO. Spanning a wide range of values of the parameters, such as the
temperature and the reactant concentration, that control the growth, our
results establish a qualitative departure from the widely accepted diffusion
controlled coarsening (Ostwald ripening) process quantified in terms of the
Lifshitz-Slyozov-Wagner theory. Further, we show that these experimental
observations can be qualitatively and quantitatively understood within a growth
mechanism that is intermediate between the two well-defined limits of diffusion
control and kinetic control.Comment: 10 pages, 4 figure
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