Effects of anisotropic scattering on electronic transport properties

The role of anisotropic scattering in transport properties is studied within the framework of the anisotropic relaxation time. The concept of the relaxation time is introduced in a rigorous way, without approximation. Its physical meaning and its connection with linear response theory is discussed. The manner in which electron-impurity scattering and electronphonon scattering influence the relaxation time is considered as well as the role of such anisotropies in the de Haas-van Alphen effect, Hall effect, deviations from Mathiessen's rule, and magnetoresistance. Examples are taken from recent experimental and theoretical work. Some common pitfalls surrounding the use of the anisotropic relaxation time are pointed out.