A Hall Effect Without Well-Defined Quasiparticles

Using a simple model of long-range impurity scattering, we illustrate how different transport and Hall relaxation rates may arise when the electron quasiparticle picture breaks down. We show how a broad and incoherent spectral function requires the use of a quantum version of the Boltzmann equation. This leads to unusual transport properties, in particular, a Hall relaxation rate which is independent of the quasiparticle scattering rate.