Spin-dependent transport in armchair carbon nanotubes and graphene nanoribbons

Nanoscience seminar by: Prof. Milena Grifoni, Universittät Regensburg, Germany

We investigate linear and nonlinear transport in interacting
single-wall carbon nanotubes and graphene nanoribbons that are weakly
attached to ferromagnetic leads. The energy spectrum of the isolated
system is obtained by starting from a microscopic model of interacting
p_z electrons. Exchange effects resulting from the short range part of
the Coulomb interaction are discussed.
Transport through the nanotube/nanoribbon quantum dots is evaluated
starting from a reduced density matrix approach, which accounts for an
arbitrarily vectored magnetization of the contacts.
We explain several striking features of the current voltage
characteristics, as e.g. current suppressions or negative differential
conductance, as a  result of the  correlations between spin states in
the quantum dot systems and leads magnetization. Effective exchange
field effects are also discussed.