Determine the temperature scale of the skewness sign change

Determine whether the sign change of the density skewness in the Fermi-Hubbard model occurs at temperatures of order the onsite interaction U, at temperatures of order the magnetic exchange scale J, or at an intermediate temperature scale of order the hopping t.

Background

The paper finds that the equilibrium density skewness changes sign as a function of hole doping in the strongly interacting Fermi-Hubbard model, with negative skewness associated with hole-like carriers and positive skewness with electron-like carriers. The authors then address the unresolved temperature dependence of this diagnostic. They contrast a quantum Monte Carlo indication that the sign change may occur near T of order U, where magnetic moments form, with spin-density-wave mean-field theory suggesting that it occurs near T of order J, where magnetic correlations develop; an intermediate scale T of order t is also possible. Resolving the relevant temperature scale would clarify how magnetic moments and magnetic correlations affect the emergence of hole- or electron-like quasiparticles and would guide experiments using cold-atom quantum simulators.

References

At finite temperature, it remains to be determined whether this sign change occurs at temperatures $T\sim U$ (as suggested by quantum Monte Carlo), which corresponds to the formation of magnetic moments, or at $T\sim J$ where magnetic correlations develop (as suggested by spin density-wave mean-field theory -- see SI), or alternatively somewhere in between ($T \sim t$).

— Characterizing quasiparticles in strongly correlated systems using nonlinear spectroscopy in quantum simulators  (2609.30124 - Skolc et al., 24 Sep 2026) in Section “Skewness and finite-temperature effects”