Fingerprints of angulon instabilities in the spectra of matrix-isolated molecules

Abstract

The formation of vortices is usually considered to be the main mechanism of angular momentum disposal in superfluids. Recently, it was predicted that a superfluid can acquire angular momentum via an alternative, microscopic route -- namely, through interaction with rotating impurities, forming so-called `angulon quasiparticles' [Phys. Rev. Lett. 114, 203001 (2015)]. The angulon instabilities correspond to transfer of a small number of angular momentum quanta from the impurity to the superfluid, as opposed to vortex instabilities, where angular momentum is quantized in units of $\hslash$ per atom. Furthermore, since conventional impurities (such as molecules) represent three-dimensional (3D) rotors, the angular momentum transferred is intrinsically 3D as well, as opposed to a merely planar rotation which is inherent to vortices. Herein we show that the angulon theory can explain the anomalous broadening of the spectroscopic lines observed for CH${}_3$ and NH${}_3$ molecules in superfluid helium nanodroplets, thereby providing a fingerprint of the emerging angulon instabilities in experiment.

7 pages + supplement

References in corpus (6)

• Spectroscopy and dynamics in helium nanodroplets
• Rotation of quantum impurities in the presence of a many-body environment
• Photoionizaton of Pure and Doped Helium Nanodroplets
• Quasiparticle approach to molecules interacting with quantum solvents
• Anomalous screening of quantum impurities by a neutral environment
• Angular self-localization of impurities rotating in a bosonic bath

Cited by in corpus (6)

• Emergence of non-abelian magnetic monopoles in a quantum impurity problem
• Molecular Impurities as a Realization of Anyons on the Two-Sphere
• A simple model for high rotational excitations of molecules in a superfluid
• Variational theory of angulons and their rotational spectroscopy
• Linear rotor in an ideal Bose gas near the threshold for binding
• Quantum rotor in a two-dimensional mesoscopic Bose gas