Momentum-Resolved Bragg Spectroscopy in Optical Lattices

TL;DR

This paper demonstrates a high-resolution, momentum-resolved Bragg spectroscopy technique to explore complex quantum phases in ultracold gases within optical lattices, revealing detailed bandstructure and interaction effects.

Contribution

It introduces a novel application of momentum-resolved Bragg spectroscopy to study excitation spectra and bandstructure in optical lattice quantum gases.

Findings

High-resolution measurement of bandstructure at various lattice depths

Identification and systematic study of interaction effects

Observation of excitation spectra in strongly correlated quantum gases

Abstract

Strongly correlated many-body systems show various exciting phenomena in condensed matter physics such as high-temperature superconductivity and colossal magnetoresistance. Recently, strongly correlated phases could also be studied in ultracold quantum gases possessing analogies to solid-state physics, but moreover exhibiting new systems such as Fermi-Bose mixtures and magnetic quantum phases with high spin values. Particularly interesting systems here are quantum gases in optical lattices with fully tunable lattice and atomic interaction parameters. While in this context several concepts and ideas have already been studied theoretically and experimentally, there is still great demand for new detection techniques to explore these complex phases in detail. Here we report on measurements of a fully momentum-resolved excitation spectrum of a quantum gas in an optical lattice by means of Bragg spectroscopy. The bandstructure is measured with high resolution at several lattice depths. Interaction effects are identified and systematically studied varying density and excitation fraction.