Effective magnetic fields in degenerate atomic gases induced by light beams with orbital angular momenta

Abstract

We investigate the influence of two resonant laser beams on the mechanical properties of degenerate atomic gases. The control and probe beams of light are considered to have Orbital Angular Momenta (OAM) and act on the three-level atoms in the Electromagnetically Induced Transparency (EIT) configuration. The theory is based on the explicit analysis of the quantum dynamics of cold atoms coupled with two laser beams. Using the adiabatic approximation, we obtain an effective equation of motion for the atoms driven to the dark state. The equation contains a vector potential type interaction as well as an effective trapping potential. The effective magnetic field is shown to be oriented along the propagation direction of the control and probe beams containing OAM. Its spatial profile can be controlled by choosing proper laser beams. We demonstrate how to generate a constant effective magnetic field, as well as a field exhibiting a radial distance dependence. The resulting effective magnetic field can be concentrated within a region where the effective trapping potential holds the atoms. The estimated magnetic length can be considerably smaller than the size of the atomic cloud.

Vortices in spin-orbit-coupled Bose-Einstein condensates

“…We are interested in finding the ground state configuration of bosons in a rotating system described by (7,17). First, we have to make an assumption about the ground state and we assume below that (at the mean-field level) all atoms occupy the same single-particle state described by the spinor wave-function, ψ ↑ (r), ψ ↓ (r) (we also call it condensate wave-function).…”

“…The key ideas underlying cold-atom spintronics -that studies particles with a synthetic spin degree of freedom coupled to their motion -grew out of the early theoretical work by Juzeliūnas et al [6][7][8][9][10][11][12], which showed that single-particle physics of atom-laser dressed states, where internal atomic states are coupled by positiondependent laser fields, can be described in terms of a non-Abelian vector potential acting on the dressed excitations. Later, it was demonstrated theoretically [13] that specific realizations of such laser configurations, including the early-proposed tripod scheme, give rise to spin-orbit-coupled Hamiltonians of Rashba-Dresselhaus type, familiar from solid-state semiconductor spintronics and that this "spintronics" description is a convenient alternative to the description in terms of the non-Abelian fields.…”

Optical lattice quantum Hall effect

“…The atoms are then confined in two-dimensional planes, of which we consider only one in the following. The artificial magnetic field term is created using one of the several methods discussed in the Introduction [34,35,36,37,38,39]. We furthermore assume that the total potential energy experienced by the atoms is given by V (p, q), where p, q label the lattice sites in the x-and y-directions, respectively.…”

Non-Abelian Gauge Potentials for Ultracold Atoms with Degenerate Dark States

“…A proper description of such a motion naturally leads to Abelian gauge potentials [9,10,11]. As shown in [12,13] a non-vanishing effective magnetic field can arise e.g. if Λ-type atoms interact with pairs of laser fields that possess a relative orbital angular momentum.…”