Multi-terminal spin-dependent transport in ballistic carbon nanotubes

We study theoretically non-local spin-transport in a ballistic carbon nanotube contacted to two ferromagnetic leads and two normal metal leads. When the magnetizations of the two ferromagnets are changed from a parallel to an antiparallel configuration, the circuit shows an hysteretic behavior which is specific to the few-channels regime. In the coherent limit, the amplitude of the magnetic signals is strongly enhanced due to resonance effects occuring inside the nanotube. Our calculations pave the way to new experiments on low-dimensional non-local spin-transport, which should give results remarkably different from the experiments realized so far in the multichannel diffusive incoherent regime.