Institute for Theoretical Physics, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht, The Netherlands.
Phys Rev Lett. 2010 Jun 4;104(22):220403. doi: 10.1103/PhysRevLett.104.220403. Epub 2010 Jun 1.
Recent experiments [Jo, Science 325, 1521 (2009)] have presented evidence of ferromagnetic correlations in a two-component ultracold Fermi gas with strong repulsive interactions. Motivated by these experiments we consider spin drag, i.e., frictional drag due to scattering of particles with opposite spin, in such systems. We show that when the ferromagnetic state is approached from the normal side, the spin drag relaxation rate is strongly enhanced near the critical point. We also determine the temperature dependence of the spin diffusion constant. In a trapped gas the spin drag relaxation rate determines the damping of the spin dipole mode, which therefore provides a precursor signal of the ferromagnetic phase transition that may be used to experimentally determine the proximity to the ferromagnetic phase.
最近的实验[Jo，Science 325, 1521 (2009)]表明，在具有强排斥相互作用的双组分超冷费米气体中存在铁磁关联。受这些实验的启发，我们考虑了这种系统中的自旋拖拽，即由于与相反自旋的粒子散射而产生的摩擦拖拽。我们表明，当铁磁态从正常侧接近时，在临界点附近，自旋拖拽弛豫率会大大增强。我们还确定了自旋扩散常数的温度依赖性。在囚禁气体中，自旋拖拽弛豫率决定了自旋偶极子模式的阻尼，因此它提供了铁磁相变的前兆信号，可用于实验确定接近铁磁相的程度。
