Excitations in two-component Bose-gases

TL;DR

This paper investigates excitations in two-component Bose gases using bosonization, Luttinger liquid theory, and dynamical DMRG, revealing spin-charge separation and analyzing experimental modifications and entanglement dynamics.

Contribution

It provides a detailed theoretical and numerical analysis of excitations and entanglement in two-component Bose gases, including experimental considerations and non-equilibrium dynamics.

Findings

Identification of spin-charge separation via spectral functions.

Quantitative agreement between analytical predictions and DMRG results.

Strong dependence of entanglement growth on initial perturbations.

Abstract

In this paper, we study a strongly correlated quantum system that has become amenable to experiment by the advent of ultracold bosonic atoms in optical lattices, a chain of two different bosonic constituents. Excitations in this system are first considered within the framework of bosonization and Luttinger liquid theory which are applicable if the Luttinger liquid parameters are determined numerically. The occurrence of a bosonic counterpart of fermionic spin-charge separation is signalled by a characteristic two-peak structure in the spectral functions found by dynamical DMRG in good agreement with analytical predictions. Experimentally, single-particle excitations as probed by spectral functions are currently not accessible in cold atoms. We therefore consider the modifications needed for current experiments, namely the investigation of the real-time evolution of density perturbations instead of single particle excitations, a slight inequivalence between the two intraspecies interactions in actual experiments, and the presence of a confining trap potential. Using time-dependent DMRG we show that only quantitative modifications occur. With an eye to the simulation of strongly correlated quantum systems far from equilibrium we detect a strong dependence of the time-evolution of entanglement entropy on the initial perturbation, signalling limitations to current reasonings on entanglement growth in many-body systems.