62 research outputs found
Electron transport and Goos-Hanchen shift in graphene with electric and magnetic barriers: optical analogy and band structure
Transport of massless Dirac fermions in graphene monolayers is analyzed in
the presence of a combination of singular magnetic barriers and applied
electrostatic potential. Extending a recently proposed (J Phys. Cond. Matt. Vol
21, 292204 (2009)) analogy between the transmission of light through a medium
with modulated refractive index and electron transmission in graphene through
singular magnetic barriers to the present case, we find the addition of a
scalar potential profoundly changes the transmission. We calculate the quantum
version of the Goos-H\"anchen shift that the electron wave suffers upon being
totally reflected by such barriers. The combined electric and magnetic barriers
substantially modify the band structure near the Dirac point. This affects
transport near the Dirac point significantly and has important consequences for
graphene-based electronics.Comment: 13 figures, Accepted version in J. Phys. Cond. Mat
Quantum Hall Solitons with Intertwined Spin and Pseudospin at $\nu = \ 1$
In this paper we study in detail different types of topological solitons
which are possible in bilayer quantum Hall systems at filling fraction
when spin degrees of freedom are included. Starting from a microscopic
Hamiltonian we derive an effective energy functional for studying such
excitations. The gauge invariance and character of this energy
fuctional and their consequences are examined. Then we identify permissible
classes of finite energy solutions which are topologically non-trivial. We also
numerically evaulate a representative solution in which a pseudospin (layer
degrees of freedom) bimeron in a given spin component is intertwined with
spin-skyrmions in each layer, and and discuss whether it is energetically
favoured as the lowest lying excitation in such system with some numerical
results.Comment: Revised version with more numerical results one more figure and table
added. Total 32 pages,6 Postscript figures. Correspondence to
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Meron Pseudospin Solutions in Quantum Hall Systems
In this paper we report calculations of some pseudospin textures for bilayer
quantum hall systems with filling factor . The textures we study are
isolated single meron solutions. Meron solutions have already been studied at
great length by others by minimising the microscopic Hamiltonian between
microscopic trial wavefunctions. Our approach is somewhat different. We
calculate them by numerically solving the nonlinear integro -differential
equations arising from extremisation of the effective action for pseudospin
textures. Our results can be viewed as augmenting earlier results and providing
a basis for comparison.Our differential equation approach also allows us to
dilineate the impact of different physical effects like the pseudospin
stiffness and the capacitance energy on the meron solution.Comment: 17 pages Revtex+ 4 Postscript figures; To appear in Int. J. Mod.
Phys.
Cavity Optomechanics with Ultra Cold Atoms in Synthetic Abelian and Non-Abelian Gauge Field
In this article we present a pedagogical discussion of some of the
optomechanical properties of a high finesse cavity loaded with ultracold atoms
in laser induced synthetic gauge fields of different types. Essentially, the
subject matter of this article is an amalgam of two sub-fields of atomic
molecular and optical (AMO) physics namely, the cavity optomechanics with
ultracold atoms and ultracold atoms in synthetic gauge field. After providing a
brief introduction to either of these fields we shall show how and what
properties of these trapped ultracold atoms can be studied by looking at the
cavity (optomechanical or transmission) spectrum. In presence of abelian
synthetic gauge field we discuss the cold-atom analogue of Shubnikov de Haas
oscillation and its detection through cavity spectrum. Then, in the presence of
a non-abelian synthetic gauge field (spin-orbit coupling), we see when the
electromagnetic field inside the cavity is quantized, it provides a quantum
optical lattice for the atoms, leading to the formation of different quantum
magnetic phases. We also discuss how these phases can be explored by studying
the cavity transmission spectrum.Comment: Invited Review Article in the journal Ato
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