Photon-assisted tunneling in optical lattices: Ballistic transport of interacting boson pairs

TL;DR

This paper investigates photon-assisted tunneling in optical lattices, revealing that bound boson pairs exhibit ballistic transport with a quadratic dependence of condensate width on tunneling, contrasting previous predictions.

Contribution

It provides analytical and numerical insights into the transition from linear to quadratic dependence in tunneling, highlighting ballistic transport of interacting boson pairs.

Findings

Condensate width scales quadratically with effective tunneling.

Ballistic transport explains the observed quadratic dependence.

Exact dispersion relations for bound pairs are derived.

Abstract

In a recent experiment [PRL 100, 040404 (2008)] an analog of photon-assisted tunneling has been observed for a Bose-Einstein condensate in an optical lattice subject to a constant force plus a sinusoidal shaking. Contrary to previous theoretical predictions, the width of the condensate was measured to be proportional to the square of the effective tunneling matrix element, rather than a linear dependence. For a simple model of two interacting bosons in a one-dimensional optical lattice, both analytical and numerical calculations indicate that such a transition from a linear to a quadratic dependence can be interpreted through the ballistic transport and the corresponding exact dispersion relation of bound boson pairs.