Bose-Fermi mixtures in 1D optical superlattices

TL;DR

This paper explores the phase diagram of boson-fermion mixtures in 1D optical superlattices at zero temperature, revealing phases like Mott-insulating and localized condensates through numerical methods.

Contribution

It introduces an adaptive basis truncation technique for exact diagonalization, enabling analysis of larger systems and revealing novel localized condensate phases.

Findings

Identification of a Mott-insulating-like phase at half filling

Discovery of a localized condensate phase due to boson-fermion interactions

Analysis of matter-wave interference and condensate fraction in phase characterization

Abstract

The zero temperature phase diagram of binary boson-fermion mixtures in two-colour superlattices is investigated. The eigenvalue problem associated with the Bose-Fermi-Hubbard Hamiltonian is solved using an exact numerical diagonalization technique, supplemented by an adaptive basis truncation scheme. The physically motivated basis truncation allows to access larger systems in a fully controlled and very flexible framework. Several experimentally relevant observables, such as the matter-wave interference pattern and the condensatefraction, are investigated in order to explore the rich phase diagram. At symmetric half filling a phase similar to the Mott-insulating phase in a commensurate purely bosonic system is identified and an analogy to recent experiments is pointed out. Furthermore a phase of complete localization of the bosonic species generated by the repulsive boson-fermion interaction is identified. These localized condensates are of a different nature than the genuine Bose-Einstein condensates in optical lattices.