Non-quasiparticle transport and resistivity saturation: A view from the large-N limit

The electron dynamics in metals are usually well described by the semiclassical approximation for long-lived quasiparticles. However, in some metals, the scattering rate of the electrons at elevated temperatures becomes comparable to the Fermi energy; then, this approximation breaks down, and the full quantum-mechanical nature of the electrons must be considered. In this talk, I will present solvable, large-N electron-phonon models, which at high temperatures enter the non-quasiparticle regime. In this regime, one of the models exhibits "resistivity saturation" to a temperature-independentvalue of the order of the quantum of resistivity - the first analytically tractable model to do so. The saturation is not due to a fundamental limit on the electron lifetime, but rather to the appearance of a a second conductivity channel. This is suggestive of the phenomenological "parallel resistor formula", known to describe the resistivity of a variety of saturating metals.

References: Phys. Rev. B 93, 075109, arXiv:1607.05725