Semiclassical theory of the spin transport of Bloch electrons

The semiclassical wave-packet theory is a powerful method in studying transport properties. Usually, the charge center of the wave-packet is used to denote the position of a semiclassical electron. In fact, wave-packets with finite size can have other centers which gives an additional degree of freedom. We develop a semiclassical theory where different centers ( e.g spin center ) can be chosen depending on which physical property (e.g spin) we are interested in. We give an example by applying this theory to calculate the spin transport.