Quasiparticle dynamics in a Bose insulator probed by inter-band Bragg spectroscopy

TL;DR

This paper explores the quasiparticle behavior in a Bose Mott insulator using inter-band Bragg spectroscopy, revealing particle-hole coherence and proposing a method to measure the spectral function akin to ARPES.

Contribution

It introduces a novel spectroscopic approach to probe the single-particle Green's function and quantum fluctuations in a Bose insulator.

Findings

Particle-hole coherence is observed in Bragg spectra.

The spectral function can be measured with momentum resolution.

Quantum fluctuations significantly influence the insulator's properties.

Abstract

We investigate experimentally and theoretically the dynamical properties of a Mott insulator in decoupled one-dimensional chains. Using a theoretical analysis of the Bragg excitation scheme we show that the spectrum of inter-band transitions holds information on the single-particle Green's function of the insulator. In particular the existence of particle-hole coherence due to quantum fluctuations in the Mott state is clearly seen in the Bragg spectra and quantified. Finally we propose a scheme to directly measure the full, momentum resolved spectral function as obtained in angle-resolved photoemission spectroscopy of solids.