Anomalous Resistivity at Weak Coupling

TL;DR

This paper investigates thermoelectric transport in a 2D Fermi-Hubbard model at weak coupling, revealing that features like linear resistivity can occur without strong correlations, challenging traditional bounds and interpretations.

Contribution

It demonstrates that linear resistivity and strange metal behaviors can emerge at weak coupling due to finite spectral width, independent of strong correlations.

Findings

Resistivity is nearly linear in temperature for T ≳ t.

No MIR bound on resistivity in single-band models.

T-linear resistivity persists down to T=0 at half filling due to nesting.

Abstract

Recent cold atom experiments have observed bad and strange metal behaviors in strongly-interacting Fermi-Hubbard systems. Motivated by these results, we calculate the thermoelectric transport properties of a 2D Fermi-Hubbard system in the weak coupling limit using quantum kinetic theory. We find that many features attributed to strong correlations are also found at weak coupling. In particular, for temperatures $T\gtrsim t$ the electrical resistivity is nearly linear in temperature despite the fact that the quasiparticle scattering rate is non-linear and changes by nearly an order of magnitude. We argue that this asymptotic behavior is a general feature of systems with a finite spectral width, which implies that there is no MIR bound on the resistivity in single-band models. Due to nesting, the $T$-linear resistivity persists down to $T=0$ at half filling. Our work sheds light on the transport regime in ultracold atom experiments, which can differ substantially from that of condensed matter systems. Disentangling these band-structure effects from the physics of strong correlations is a major challenge for future experiments.