Hybrid matter-wave-microwave solitons produced by the local-field effect

TL;DR

This paper introduces a novel magnetic local-field effect mechanism that couples spinor Bose-Einstein condensates to microwaves, leading to the formation of stable hybrid matter-wave-microwave solitons with potential applications in atom lasers.

Contribution

It develops a theoretical framework for magnetic LFE coupling in BECs, revealing a new long-range interaction that enables stable solitons despite strong inter-component repulsion.

Findings

Magnetic LFE induces short-range attraction and long-range interaction.

Long-range interaction causes modulational instability of uniform states.

Stable hybrid matter-wave-microwave solitons are predicted, smaller than MW wavelength.

Abstract

It was recently found that the electric local-field effect (LFE) can lead to strong coupling of atomic Bose-Einstein condensates (BECs) to off-resonant optical fields. We demonstrate that the magnetic LFE gives rise to a previously unexplored mechanism for coupling a (pseudo) spinor BEC or fermion gas to microwaves (MWs). We present a theory for the magnetic LFE, and find that it gives rise to a short-range attractive interaction between two components of the (pseudo) spinor, and a long-range interaction between them. The latter interaction, resulting from deformation of the magnetic field, is locally repulsive but globally attractive, in sharp contrast with its counterpart for the optical LFE, produced by phase modulation of the electric field. Our analytical results, confirmed by the numerical computations, show that the long-range interaction gives rise to modulational instability of the spatially uniform state, and creates stable ground states in the form of hybrid matter-wave-microwave solitons (which seem like one-dimensional magnetic monopoles), with a size much smaller than the MW wavelength, even in the presence of arbitrarily strong contact inter-component repulsion. The setting is somewhat similar to exciton-polaritonic condensates in semiconductor microcavities. The release of matter waves from the soliton may be used for the realization of an atom laser. The analysis also applies to molecular BECs with rotational states coupled by the electric MW field.