Kinetic Thomas–Fermi solutions of the Gross–Pitaevskii equation

Abstract

Approximate solutions of the Gross–Pitaevskii (GP) equation, obtained upon neglection of the kinetic energy, are well known as Thomas–Fermi solutions. They are characterized by the compensation of the local potential by the collisional energy. In this article we consider exact solutions of the GP-equation with this property and definite values of the kinetic energy, which suggests the term ‘‘kinetic Thomas– Fermi” (KTF) solutions. Despite their formal simplicity, KTF-solutions can possess complex current density fields with unconventional topology. We point out that a large class of light-shift potentials gives rise to KTF-solutions. As elementary examples, we consider one-dimensional and two-dimensional optical lattice scenarios, obtained by means of the superposition of two, three and four laser beams, and discuss the stability properties of the corresponding KTF-solutions. A general method is proposed to excite twodimensional KTF-solutions in experiments by means of time-modulated light-shift potentials.