Do mixtures of bosonic and fermionic atoms adiabatically heat up in optical lattices?

TL;DR

This paper studies how mixing bosonic and fermionic atoms in optical lattices affects their temperature during adiabatic lattice ramp-up, revealing that fermions cause the mixture to heat up more than pure bosons, impacting experimental interpretations.

Contribution

It provides a theoretical analysis of intrinsic heating effects in boson-fermion mixtures during optical lattice loading, combining multiple approximation methods for different regimes.

Findings

Fermions cause the mixture to heat up more than pure bosons during lattice ramp-up.

The temperature after ramp-up is always higher in the mixture, affecting experimental outcomes.

The analysis aligns with recent experimental observations.

Abstract

Mixtures of bosonic and fermionic atoms in optical lattices provide a promising arena to study strongly correlated systems. In experiments realizing such mixtures in the quantum degenerate regime the temperature is a key parameter. In this work, we investigate the intrinsic heating and cooling effects due to an entropy-preserving raising of the optical lattice potential. We analyze this process, identify the generic behavior valid for a wide range of parameters, and discuss it quantitatively for the recent experiments with 87Rb and 40K atoms. In the absence of a lattice, we treat the bosons in the Hartree-Fock-Bogoliubov-Popov-approximation, including the fermions in a self-consistent mean field interaction. In the presence of the full three-dimensional lattice, we use a strong coupling expansion. As a result of the presence of the fermions, the temperature of the mixture after the lattice ramp-up is always higher than for the pure bosonic case. This sheds light onto a key point in the analysis of recent experiments.