7 research outputs found
Which Kubo formula gives the exact conductance of a mesoscopic disordered system?
In both research and textbook literature one often finds two ``different''
Kubo formulas for the zero-temperature conductance of a non-interacting Fermi
system. They contain a trace of the product of velocity operators and
single-particle (retarded and advanced) Green operators: or . The study investigates the relationship between
these expressions, as well as the requirements of current conservation, through
exact evaluation of such quantum-mechanical traces for a nanoscale (containing
1000 atoms) mesoscopic disordered conductor. The traces are computed in the
semiclassical regime (where disorder is weak) and, more importantly, in the
nonperturbative transport regime (including the region around
localization-delocalization transition) where concept of mean free path ceases
to exist. Since quantum interference effects for such strong disorder are not
amenable to diagrammatic or nonlinear -model techniques, the evolution
of different Green function terms with disorder strength provides novel insight
into the development of an Anderson localized phase.Comment: 7 pages, 5 embedded EPS figures, final published version (note: PRB
article has different title due to editorial censorship
Spin-filtering and charge- and spin-switching effects in a quantum wire with periodically attached stubs
Spin-dependent electron transport in a periodically stubbed quantum wire in
the presence of Rashba spin-orbit interaction (SOI) is studied via the
nonequilibrium Green's function method combined with the Landauer-Buttiker
formalism. The coexistence of spin filtering, charge and spin switching are
found in the considered system. The mechanism of these transport properties is
revealed by analyzing the total charge density and spin-polarized density
distributions in the stubbed quantum wire. Furthermore, periodic spin-density
islands with high polarization are also found inside the stubs, owing to the
interaction between the charge density islands and the Rashba SOI-induced
effective magnetic field. The proposed nanostructure may be utilized to devise
an all-electrical multifunctional spintronic device.Comment: 4 pages, 4 figure