169 research outputs found
Time-dependent current density functional theory via time-dependent deformation functional theory: A constrained search formulation in the time domain
The logical structure and the basic theorems of time-dependent current
density functional theory (TDCDFT) are analyzed and reconsidered from the point
of view of recently proposed time-dependent deformation functional theory
(TDDefFT). It is shown that the formalism of TDDefFT allows to avoid a
traditional external potential-to-density/current mapping. Instead the theory
is formulated in a form similar to the constrained search procedure in the
ground state DFT. Within this formulation of TDCDFT all basic functionals
appear from the solution of a constrained universal many-body problem in a
comoving reference frame, which is equivalent to finding a conditional extremum
of a certain universal action functional. As a result the physical origin of
the universal functionals entering the theory, as well as their proper causal
structure becomes obvious. In particular, this leaves no room for any doubt
concerning predictive power of the theory.Comment: revtex4, 24 page
Orbital momentum Hall effect in p-doped graphane
It is shown that an electric field applied to p-doped graphane generates a
dissipationless orbital momentum Hall current. In the clean limit the
corresponding Hall conductivity is independent of the concentration of holes.
The Hall effect is related to the -Berry phase accumulated when heavy and
light holes are transported around the degeneracy point in the center of the
Brillouin zone. This also leads to the orbital momentum edge currents in the
equilibrium state, and to the accumulation of the orbital momentum at the edges
when the system is driven out of equilibrium.Comment: RevTeX 4, 4 pages, 2 figures, final versio
Singlet-triplet conversion and the long-range proximity effect in superconductor-ferromagnet structures with generic spin dependent fields
The long-range proximity effect in superconductor/ferromagnet (S/F) hybrid
nano-structures is observed if singlet Cooper pairs from the superconductor are
converted into triplet pairs which can diffuse into the fer- romagnet over
large distances. It is commonly believed that this happens only in the presence
of magnetic inhomogeneities. We show that there are other sources of the
long-range triplet component (LRTC) of the con- densate and establish general
conditions for their occurrence. As a prototypical example we consider first a
system where the exchange field and spin-orbit coupling can be treated as time
and space components of an effective SU(2) potential. We derive a SU(2)
covariant diffusive equation for the condensate and demonstrate that an
effective SU(2) electric field is responsible for the long-range proximity
effect. Finally, we extend our analysis to a generic ferromagnet and establish
a universal condition for the LRTC. Our results open a new avenue in the search
for such correlations in S/F structures and make a hitherto unknown connection
between the LRTC and Yang-Mills electrostatics.Comment: 5 pages; 1 Figure; updated file with new reference
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