Transmittivity of a Bose-Einstein condensate on a lattice: interference from period doubling and the effect of disorder

TL;DR

This paper investigates how period doubling and disorder affect the transmittivity of a Bose-Einstein condensate in a lattice, revealing interference patterns and the impact of fermionic configurations on transport properties.

Contribution

It introduces a model for analyzing transmittivity in a Bose-Einstein condensate with period doubling and disorder, highlighting the effects on interference patterns and tunneling.

Findings

Period doubling creates a new band gap and interference pattern.

Disorder washes out the interference pattern.

Numerical results for Rb-K mixture demonstrate these effects.

Abstract

We evaluate the particle current flowing in steady state through a Bose-Einstein condensate subject to a constant force in a quasi-onedimensional lattice and to attractive interactions from fermionic atoms that are localized in various configurations inside the lattice wells. The system is treated within a Bose-Hubbard tight binding model by an out-of-equilibrium Green's function approach. A new band gap opens up when the lattice period is doubled by locating the fermions in alternate wells and yields an interference pattern in the transmittivity on varying the intensity of the driving force. The positions of the transmittivity minima are determined by matching the period of Bloch oscillations and the time for tunnelling across the band gap. Massive disorder in the distribution of the fermions will wash out the interference pattern, but the same period doubling of the lattice can be experimentally realized in a four-beam set-up. We report illustrative numerical results for a mixture of 87Rb and 40K atoms in an optical lattice created by laser beams with a wavelength of 763 nm.