Self-Trapping of Bosons and Fermions in Optical Lattices

TL;DR

This paper theoretically explores how attractive interactions between bosons and fermions in optical lattices lead to self-trapping of bosons, significant deformation of potential landscapes, and shifts in phase transition points, highlighting the importance of higher Bloch bands.

Contribution

It reveals the nonlinear effects of boson-fermion interactions on localization and phase transitions, emphasizing the role of higher Bloch bands in quantum gas mixtures.

Findings

Bosons exhibit self-trapping due to fermionic attraction.

Fermion orbitals are significantly squeezed, deforming the bosonic potential.

Critical potential depth depends nonlinearly on interaction strength.

Abstract

We theoretically investigate the enhanced localization of bosonic atoms by fermionic atoms in three-dimensional optical lattices and find a self-trapping of the bosons for attractive boson-fermion interaction. Because of this mutual interaction, the fermion orbitals are substantially squeezed, which results in a strong deformation of the effective potential for bosons. This effect is enhanced by an increasing bosonic filling factor leading to a large shift of the transition between the superfluid and the Mott-insulator phase. We find a nonlinear dependency of the critical potential depth on the boson-fermion interaction strength. The results, in general, demonstrate the important role of higher Bloch bands for the physics of attractively interacting quantum gas mixtures in optical lattices and are of direct relevance to recent experiments with 87Rb - 40K mixtures, where a large shift of the critical point has been found.