Phases of a Bose-Einstein condensate of microwave-shielded dipolar molecules

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Main Authors: Polterauer, Chiara J., Zillich, Robert E.
Format: Preprint
Published: 2025
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author Polterauer, Chiara J.
Zillich, Robert E.
author_facet Polterauer, Chiara J.
Zillich, Robert E.
contents Bose-Einstein condensation of dipolar molecules can be achieved by shielding loss channels with microwave fields. The microwave coupling can be approximated by effective dipole-dipole interactions with a short-range repulsion. We study properties and stability of these molecular Bose gases with a many-body variational method, the hypernetted-chain Euler-Lagrange method for a wide range of densities and repulsion strengths of the microwave shield. We find a homogeneous gas-like phase which, however, is unstable at low density against density waves: at a critical density, which depends on the repulsion strength, the dipolar fluid undergoes a phase transition to a layer phase. Thus, if the molecular condensate is expanded adiabatically by decreasing the confinement strength, it will spontaneously form layers at the critical density. These quasi-two-dimensional layers can be self-bound, hence form two-dimensional liquids. By varying the microwave shield, the predicted equilibrium densities span more than an order of magnitude.
format Preprint
id arxiv_https___arxiv_org_abs_2507_18986
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Phases of a Bose-Einstein condensate of microwave-shielded dipolar molecules
Polterauer, Chiara J.
Zillich, Robert E.
Quantum Gases
Bose-Einstein condensation of dipolar molecules can be achieved by shielding loss channels with microwave fields. The microwave coupling can be approximated by effective dipole-dipole interactions with a short-range repulsion. We study properties and stability of these molecular Bose gases with a many-body variational method, the hypernetted-chain Euler-Lagrange method for a wide range of densities and repulsion strengths of the microwave shield. We find a homogeneous gas-like phase which, however, is unstable at low density against density waves: at a critical density, which depends on the repulsion strength, the dipolar fluid undergoes a phase transition to a layer phase. Thus, if the molecular condensate is expanded adiabatically by decreasing the confinement strength, it will spontaneously form layers at the critical density. These quasi-two-dimensional layers can be self-bound, hence form two-dimensional liquids. By varying the microwave shield, the predicted equilibrium densities span more than an order of magnitude.
title Phases of a Bose-Einstein condensate of microwave-shielded dipolar molecules
topic Quantum Gases
url https://arxiv.org/abs/2507.18986