Spin drag and spin-charge separation in cold fermi gases.
Low-energy spin and charge excitations of one-dimensional interacting fermions are completely decoupled and propagate with different velocities. These modes, however, can decay due to several possible mechanisms. In this Letter we expose a new facet of spin-charge separation: not only the speeds but also the damping rates of spin and charge excitations are different. While the propagation of long-wavelength charge excitations is essentially ballistic, spin propagation is intrinsically damped and diffusive. We suggest that cold Fermi gases trapped inside a tight atomic waveguide offer the opportunity to measure the spin-drag relaxation rate that controls the broadening of a spin packet.
NEST-CNR-INFM and Scuola Normale Superiore, I-56126 Pisa, Italy. m.polini@sns.it
Marco
M
Polini
Giovanni
G
Vignale