Momentum Resolved Optical Lattice Modulation Spectroscopy for Bose Hubbard Model

TL;DR

This paper introduces a novel optical lattice modulation spectroscopy technique to analyze the spectral functions of ultracold bosons, enabling phase identification and transition detection in Bose-Hubbard systems.

Contribution

It presents a new method to measure momentum-resolved spectral functions in ultracold bosons, distinguishing features of different quantum phases via lattice modulation.

Findings

In the Mott phase, it reveals momentum-dependent excitation gaps.

In the superfluid phase, it maps Bogoliubov quasiparticle spectra.

The response evolution with frequency identifies quantum phases.

Abstract

We propose a new method of optical lattice modulation spectroscopy for studying the spectral function of ultracold bosons in an optical lattice. We show that different features of the single particle spectral function in different quantum phases can be obtained by measuring the change in momentum distribution after the modulation. In the Mott phase, this gives information about the momentun dependent gap to particle-hole excitations as well as their spectral weight. In the superfluid phase, one can obtain the spectrum of the gapless Bogoliubov quasiparticles as well as the gapped amplitude fluctuations. The distinct evolution of the response with modulation frequency in the two phases can be used to identify these phases and the quantum phase transition separating them.