Simultaneous slow phase and group velocities of light in an anisotropic   metamaterial
  We study theoretically the effect of ultraslow phase and group velocities in an anisotropic metamaterial. The ultraslow phase propagation is induced by the hyperbolic dispersion relation. While the inherent physics underlying the slow group velocity are collective operations of the frequency and spatial dispersion. We show that a Gaussian wave packet exhibits simultaneous slow phase and group velocities which depend on the choice of incident angles and principal axis angles. The anisotrocpic metamaterial slab can be constructed and the ultraslow phase and group velocities can be measured experimentally. 
Hailu Luo, Zhongzhou Ren, Weixing Shu, Fei Li