Spin Waves in a Bose-Einstein–Condensed Atomic Spin Chain

Abstract

The spin dynamics of atomic Bose-Einstein condensates confined in a one-dimensional optical lattice is studied. The condensates at each lattice site behave like spin magnets that can interact with each other through both the light-induced dipole-dipole interaction and the static magnetic dipole-dipole interaction. We show how these site-to-site dipolar interactions can distort the ground-state spin orientations and lead to the excitation of spin waves. The dispersion relation of the spin waves is studied and possible detection schemes are proposed.

Collective magnetism in arrays of spinor Bose–Einstein condensates

“…Therefore, the time-averaged magnetization is close to zero. The MC solution for the ground state of a 2D square lattice of pure dipoles (spherical BECs) is identical to the solution a = b of [14]. Inclusion of the shape anisotropy for spheroids with c > 2a transforms this pattern into the checkerboard 2 × 2 out-of-plane configuration for any multipole rank.…”

“…First, we discuss the thermodynamically stable states of linear chains of pancake-like BECs. In contrast to [9,14], the Hamiltonian we use includes an additional anisotropy term +K S 2…”

“…We first discuss the energy scales and their geometry dependence. In analogy to [10,14], we consider a one-dimensional (1D) or 2D array of ferromagnetic mini-spinor condensates at negligible external magnetic field. The term ferromagnetic refers to the local contact interaction between atoms mediated by spin-dependent s-wave collisions [15,16], which give rise to a mean-field energy minimum for aligned spins.…”

“…We find that the shape anisotropy of a ferromagnetic mini-condensate dominates over the inter-condensate interactions if the long axis 2c of a spheroid is > √ 2 times larger than its short axis 2a. For that reason, the ground states of realistic BEC arrays differ from those predicted in [10,14] and show non-trivial structures, such as spin spirals. Furthermore, we predict the ground state of a two-dimensional (2D) square array of spin-domain condensates [13].…”

Superfluid–Mott-insulator transition of spin-1 bosons in optical resonators

“…On the other hand, the spin-dependent collision interactions allow for the population exchange among hyperfine spin states. Rich physics have been disclosed in this system, such as the novel phases [4,5], superfluid-Mottinsulator (MI) transition [6,7], ferromagnetism [8], and spin waves [9].…”