Multi-band spectroscopy of ultracold fermions: Observation of reduced tunneling in attractive Bose-Fermi mixtures

TL;DR

This paper presents a detailed experimental study of ultracold fermions in optical lattices, revealing how attractive Bose-Fermi interactions reduce tunneling energies through self-trapping effects.

Contribution

It introduces a novel multi-band spectroscopy technique for fermionic atoms and demonstrates interaction-induced tunneling suppression in Bose-Fermi mixtures.

Findings

High-precision measurement of band structure and tunneling energies

Observation of tunneling reduction dependent on atom number ratio

Attribution of tunneling suppression to interaction-induced lattice depth increase

Abstract

We perform a detailed experimental study of the band excitations and tunneling properties of ultracold fermions in optical lattices. Employing a novel multi-band spectroscopy for fermionic atoms we can measure the full band structure and tunneling energy with high accuracy. In an attractive Bose-Fermi mixture we observe a significant reduction of the fermionic tunneling energy, which depends on the relative atom numbers. We attribute this to an interaction-induced increase of the lattice depth due to self-trapping of the atoms.