Intermolecular forces and correlations mediated by a phonon bath.

Area of Science:

• Quantum Chemistry
• Condensed Matter Physics
• Atomic and Molecular Physics

Background:

• Helium nanodroplets offer a unique environment for studying chemical reactivity.
• Understanding interactions between molecules in a bosonic bath is crucial for quantum simulations.

Purpose of the Study:

• To investigate the effective interaction and correlations between two diatomic molecules in a helium nanodroplet.
• To introduce and characterize a new quasiparticle, the biangulon, arising from these interactions.

Main Methods:

• Born-Oppenheimer approximation to study intermolecular interaction dependence on rotational states.
• One-phonon excitation variational ansatz for weak-coupling regime analysis and energy spectrum.
• Diagonalization scheme using angulon and impurity wave functions to study the transition to biangulon formation.

Main Results:

• Introduction of the biangulon quasiparticle, analogous to the bipolaron, formed by two interacting rotating molecules.
• Demonstration of strong molecular alignment in the ground state within the strong-coupling regime.
• Identification of shifted angulon instabilities and a novel spectral instability in the biangulon, indicating resonant angular momentum transfer.

Conclusions:

• The biangulon quasiparticle exhibits distinct features, including unique instabilities, proposed as experimental signatures.
• The study provides a theoretical framework to describe the transition from separated angulons to the biangulon state.
• This research opens avenues for experimental manipulation and observation of complex molecular interactions in quantum environments.