Variational theory of angulons and their rotational spectroscopy
arXiv:2211.08070 · doi:10.1063/5.0135893
Abstract
The angulon, a quasiparticle formed by a quantum rotor dressed by the excitations of a many-body bath, can be used to describe an impurity rotating in a fluid or solid environment. Here we propose a coherent state ansatz in the co-rotating frame which provides a comprehensive theoretical description of angulons. We reveal the quasiparticle properties, such as energies, quasiparticle weights and spectral functions, and show that our ansatz yields a persistent decrease in the impurity's rotational constant due to many-body dressing, consistent with experimental observations. From our study, a picture of the angulon emerges as an effective spin interacting with a magnetic field that is self-consistently generated by the molecule's rotation. Moreover, we discuss rotational spectroscopy, which focuses on the response of rotating molecules to a laser perturbation in the linear response regime. Importantly, we take into account initial-state interactions that have been neglected in prior studies and reveal their impact on the excitation spectrum. To examine the angulon instability regime, we use a single-excitation ansatz and obtain results consistent with experiments, in which a broadening of spectral lines is observed while phonon wings remain highly suppressed due to initial-state interactions.
References in corpus (26)
- Observation of Attractive and Repulsive Polarons in a Bose-Einstein Condensate
- Bose polarons in the strongly interacting regime
- Spectroscopy and dynamics in helium nanodroplets
- Helium nanodroplet isolation ro-vibrational spectroscopy: methods and recent results
- Time dependent impurity in ultracold fermions: orthogonality catastrophe and beyond
- Quantum dynamics of ultracold Bose polarons
- Universal many-body response of heavy impurities coupled to a Fermi sea
- Rotation of quantum impurities in the presence of a many-body environment
- Variational Study of Fermionic and Bosonic Systems with Non-Gaussian States: Theory and Applications
- Impulsive Laser Induced Alignment of Molecules Dissolved in Helium Nanodroplets
- Quasiparticle approach to molecules interacting with quantum solvents
- Deformation of a quantum many-particle system by a rotating impurity
- Polaronic mass renormalization of impurities in BEC: correlated Gaussian wavefunction approach
- Roton-Rotation Coupling of Acetylene in He
- Zero-Temperature Phases of the 2D Hubbard-Holstein Model: A Non-Gaussian Exact Diagonalization Study
- Quantum Rotation of HCN and DCN in Helium-4
- Quantum many-body dynamics of the Einstein-de Haas effect
- Emergence of non-abelian magnetic monopoles in a quantum impurity problem
- Rotation of cold molecular ions inside a Bose-Einstein condensate
- Fingerprints of angulon instabilities in the spectra of matrix-isolated molecules
- Diagrammatic Monte Carlo approach to angular momentum in quantum many-particle systems
- Anomalous screening of quantum impurities by a neutral environment
- Diagrammatic approach to orbital quantum impurities interacting with a many-particle environment
- Excited rotational states of molecules in a superfluid
- A simple model for high rotational excitations of molecules in a superfluid
- Rotational cooling of molecules in a Bose-Einstein-Condensate