Incoherent regimes around the Mott point

Transport regimes without coherent quasiparticles have recently attracted much attention. Here, we explore the incoherent regimes of the single-band Hubbard model using a semi-classical approximation for Hubbard-Stratonovich fields that represent electron-electron scattering. We show that most finite-temperature behavior outside the quasiparticle regime can be described in terms of the quasi-elastic scattering picture of a properly defined thermal disorder potential. We also discuss how to avoid some unphysical aspects of a naively formulated semi-classical formulation to capture some aspects of the intermediate-temperature quantum critical regime and the Bad Metal behavior at high temperatures. We conclude that transport around the Mott-Ioffe-Regel limit has essentially a semi-classical character, where coherent quasiparticles simply do not exist.