Thermopower of the Hubbard model: Effects of multiple orbitals and magnetic fields in the atomic limit

TL;DR

This paper derives exact formulas for thermopower in the multi-orbital Hubbard model in the atomic limit, exploring temperature and magnetic field effects, including spikes in thermopower due to magnetic fields.

Contribution

It provides the first exact expressions for thermopower in the multi-orbital Hubbard model in the atomic limit, including magnetic field effects and temperature dependence.

Findings

Thermopower reduces to Heikes formula in high and low-temperature limits.

Temperature dependence of thermopower is obtained across regimes.

Magnetic field induces spikes in thermopower at specific field values.

Abstract

We consider strongly-correlated systems described by the multi-orbital Hubbard model in the atomic limit and obtain exact expressions for the chemical potential and thermopower. We show that these expressions reduce to the Heikes formula in the appropriate limits ($k_BT \gg U$) and ($k_BT \ll U$) and obtain the full temperature dependence in between these regimes. We also investigate the effect of a magnetic field introduced through a Zeeman term and observe that the thermopower of the multi-orbital Hubbard model displays spikes as a function of magnetic field at certain special values of the field. This effect might be observable in experiments for materials with a large magnetic coupling.