Intermolecular forces and correlations mediated by a phonon bath

Abstract

Inspired by the possibility to experimentally manipulate and enhance chemical reactivity in helium nanodroplets, we investigate the effective interaction and the resulting correlations between two diatomic molecules immersed in a bath of bosons. By analogy with the bipolaron, we introduce the \emph{biangulon} quasiparticle describing two rotating molecules that align with respect to each other due to the effective attractive interaction mediated by the excitations of the bath. We study this system in different parameter regimes and apply several theoretical approaches to describe its properties. Using a Born-Oppenheimer approximation, we investigate the dependence of the effective intermolecular interaction on the rotational state of the two molecules. In the strong-coupling regime, a product-state ansatz shows that the molecules tend to have a strong alignment in the ground state. To investigate the system in the weak-coupling regime, we apply a one-phonon excitation variational ansatz, which allows us to access the energy spectrum. In comparison to the angulon quasiparticle, the biangulon shows shifted angulon instabilities and an additional spectral instability, where resonant angular momentum transfer between the molecules and the bath takes place. These features are proposed as an experimentally observable signature for the formation of the biangulon quasiparticle. Finally, by using products of single angulon and bare impurity wave functions as basis states, we introduce a diagonalization scheme that allows us to describe the transition from two separated angulons to a biangulon as a function of the distance between the two molecules.

14 pages, 8 figures

References in corpus (9)

• Rotation of quantum impurities in the presence of a many-body environment
• Quasiparticle approach to molecules interacting with quantum solvents
• Bipolarons and multi-polarons consisting of impurity atoms in a Bose-Einstein condensate
• Emergence of non-abelian magnetic monopoles in a quantum impurity problem
• Fingerprints of angulon instabilities in the spectra of matrix-isolated molecules
• Impurity crystal in a Bose-Einstein condensate
• Anomalous screening of quantum impurities by a neutral environment
• Formation of polaron clusters
• Far-from-equilibrium dynamics of angular momentum in a quantum many-particle system

Cited by in corpus (6)

• Observation of a smooth polaron-molecule transition in a degenerate Fermi gas
• Molecule-photon interactions in phononic environments
• An impurity in a heteronuclear two-component Bose mixture
• Impurities in a one-dimensional Bose gas: the flow equation approach
• Molecular Impurities as a Realization of Anyons on the Two-Sphere
• Diagrammatic Monte Carlo for electronic correlation in molecules: high-order many-body perturbation theory with low scaling