Spectroscopy of ultracold atoms by periodic lattice modulations

TL;DR

This paper introduces a non-perturbative method using time-dependent density-matrix renormalization group to analyze how periodic lattice modulations probe ultracold bosons, revealing sharp energy absorption peaks across different phases.

Contribution

It demonstrates that energy absorption peaks occur in both Mott insulators and superfluids, providing new experimental measures for interaction strength and incommensurability.

Findings

Sharp peaks are present in superfluids at incommensurate filling.

Peak structure correlates with interaction strength.

Second peak height indicates incommensurability.

Abstract

We present a non-perturbative analysis of a new experimental technique for probing ultracold bosons in an optical lattice by periodic lattice depth modulations. This is done using the time-dependent density-matrix renormalization group method. We find that sharp energy absorption peaks are not unique to the Mott insulating phase at commensurate filling, but also exist for superfluids at incommensurate filling. For strong interactions the peak structure provides an experimental measure of the interaction strength. Moreover, the peak height of the second peak can be employed as a measure of the incommensurability of the system.