184 research outputs found
Persistent current of relativistic electrons on a Dirac ring in presence of impurities
We study the behavior of persistent current of relativistic electrons on a
one dimensional ring in presence of attractive/repulsive scattering potentials.
In particular, we investigate the persistent current in accordance with the
strength as well as the number of the scattering potential. We find that in
presence of single scatterer the persistent current becomes smaller in
magnitude than the scattering free scenario. This behaviour is similar to the
non-relativistic case. Even for a very strong scattering potential, finite
amount of persistent current remains for a relativistic ring. In presence of
multiple scatterer we observe that the persistent current is maximum when the
scatterers are placed uniformly compared to the current averaged over random
configurations. However if we increase the number of scatterers, we find that
the random averaged current increases with the number of scatterers. The latter
behaviour is in contrast to the non-relativistic case.Comment: This is the published versio
Conductance, Valley and Spin polarization and Tunnelling magneto-resistance in ferromagnetic-normal-ferromagnetic junctions of silicene
We investigate charge conductance and spin and valley polarization along with
the tunnelling magneto-resistance (TMR) in silicene junctions composed of
normal silicene and ferromagnetic silicene. We show distinct features of the
conductances for parallel and anti-parallel spin configurations and the TMR, as
the ferromagnetic-normal-ferromagnetic (FNF) junction is tuned by an external
electric field. We analyse the behavior of the charge conductance and valley
and spin polarizations in terms of the independent conductances of the
different spins at the two valleys and the band structure of ferromagnetic
silicene and show how the conductances are affected by the vanishing of the
propagating states at one or the other valley. In particular, unlike in
graphene, the band structure at the two valleys are independently affected by
the spin in the ferromagnetic regions and lead to non-zero, and in certain
parameter regimes, pure valley and spin polarizations, which can be tuned by
the external electric field. We also investigate the oscillatory behavior of
the TMR with respect to the strength of the barrier potential (both
spin-independent and spin-dependent barriers) in the normal silicene region and
note that in some parameter regimes, the TMR can even go from positive to
negative values, as a function of the external electric field.Comment: This is the published versio
Spintronics with NSN Junction of one-dimensional quantum wires : A study of Pure Spin Current and Magnetoresistance
We demonstrate possible scenarios for production of pure spin current and
large tunnelling magnetoresistance ratios from elastic co-tunnelling and
crossed Andreev reflection across a superconducting junction comprising of
normal metal-superconductor-normal metal, where, the normal metal is a
one-dimensional interacting quantum wire. We show that there are fixed points
in the theory which correspond to the case of pure spin current. We analyze the
influence of electron-electron interaction and see how it stabilizes or
de-stabilizes the production of pure spin current. These fixed points can be of
direct experimental relevance for spintronics application of normal
metal-superconductor-normal metal junctions of one-dimensional quantum wires.
We also calculate the power law temperature dependence of the crossed Andreev
reflection enhanced tunnelling magnetoresistance ratio for the normal
metal-superconductor-normal metal junction.Comment: Final version to appear in Euro. Phys. Let
A systematic stability analysis of the renormalisation group flow for the normal-superconductor-normal junction of Luttinger liquid wires
We study the renormalization group flows of the two terminal conductance of a
superconducting junction of two Luttinger liquid wires. We compute the power
laws associated with the renormalization group flow around the various fixed
points of this system using the generators of the SU(4) group to generate the
appropriate parameterization of a S-matrix representing small deviations from a
given fixed point S-matrix (obtained earlier in Phys. Rev. B 77, 155418
(2008)), and we then perform a comprehensive stability analysis. In particular,
for the non-trivial fixed point which has intermediate values of transmission,
reflection, Andreev reflection and crossed Andreev reflection, we show that
there are eleven independent directions in which the system can be perturbed,
which are relevant or irrelevant, and five directions which are marginal. We
obtain power laws associated with these relevant and irrelevant perturbations.
Unlike the case of the two-wire charge-conserving junction, here we show that
there are power laws which are non-linear functions of V(0) and V(2k_{F})
(where V(k) represents the Fourier transform of the inter-electron interaction
potential at momentum k). We also obtain the power law dependence of linear
response conductance on voltage bias or temperature around this fixed point.Comment: Final version to appear in Phys. Rev.
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