1,371,556 research outputs found
Transport Properties of Solitons
We calculate in this article the transport coefficients which characterize
the dynamics of solitons in quantum field theory using the methods of
dissipative quantum systems. We show how the damping and diffusion coefficients
of soliton-like excitations can be calculated using the integral functional
formalism. The model obtained in this article has new features which cannot be
obtained in the standard models of dissipation in quantum mechanics.Comment: 16 Pages, RevTeX, Preprint UIU
Chalker-Coddington model described by an S-matrix with odd dimensions
The Chalker-Coddington network model is often used to describe the transport
properties of quantum Hall systems. By adding an extra channel to this model,
we introduce an asymmetric model with profoundly different transport
properties. We present a numerical analysis of these transport properties and
consider the relevance for realistic systems.Comment: 7 pages, 4 figures. To appear in the EP2DS-17 proceeding
The temperature dependence of FeRh’s transport properties
The finite-temperature transport properties of FeRh compounds are investigated by first-principles
Density Functional Theory-based calculations. The focus is on the behavior of the longitudinal resistivity
with rising temperature, which exhibits an abrupt decrease at the metamagnetic transition
point, T = Tm between ferro- and antiferromagnetic phases. A detailed electronic structure investigation
for T ≥ 0 K explains this feature and demonstrates the important role of (i) the difference
of the electronic structure at the Fermi level between the two magnetically ordered states and (ii)
the different degree of thermally induced magnetic disorder in the vicinity of Tm, giving different
contributions to the resistivity. To support these conclusions, we also describe the temperature
dependence of the spin-orbit induced anomalous Hall resistivity and Gilbert damping parameter.
For the various response quantities considered the impact of thermal lattice vibrations and spin fluctuations
on their temperature dependence is investigated in detail. Comparison with corresponding
experimental data finds in general a very good agreement
Transport properties of single atoms
We present a systematic study of the ballistic electron conductance through
sp and 3d transition metal atoms attached to copper and palladium crystalline
electrodes. We employ the 'ab initio' screened Korringa-Kohn-Rostoker Green's
function method to calculate the electronic structure of nanocontacts while the
ballistic transmission and conductance eigenchannels were obtained by means of
the Kubo approach as formulated by Baranger and Stone. We demonstrate that the
conductance of the systems is mainly determined by the electronic properties of
the atom bridging the macroscopic leads. We classify the conducting
eigenchannels according to the atomic orbitals of the contact atom and the
irreducible representations of the symmetry point group of the system that
leads to the microscopic understanding of the conductance. We show that if
impurity resonances in the density of states of the contact atom appear at the
Fermi energy, additional channels of appropriate symmetry could open. On the
other hand the transmission of the existing channels could be blocked by
impurity scattering.Comment: RevTEX4, 9 pages, 9 figure
Robust Transport Properties in Graphene
Two-dimensional Dirac fermions are used to discuss quasiparticles in graphene
in the presence of impurity scattering. Transport properties are completely
dominated by diffusion. This may explain why recent experiments did not find
weak localization in graphene. The diffusion coefficient of the quasiparticles
decreases strongly with increasing strength of disorder. Using the Kubo
formalism, however, we find a robust minimal conductivity that is independent
of disorder. This is a consequence of the fact that the change of the diffusion
coefficient is fully compensated by a change of the number of delocalized
quasiparticle states.Comment: 4 pages, 1 figur
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