title: Rotation of Quantum Impurities in the Presence of a Many-Body Environment.
abstract: We develop a microscopic theory describing a quantum impurity whose rotational degree of freedom is coupled to a many-particle bath. We approach the problem by introducing the concept of an "angulon"-a quantum rotor dressed by a quantum field-and reveal its quasiparticle properties using a combination of variational and diagrammatic techniques. Our theory predicts renormalization of the impurity rotational structure, such as that observed in experiments with molecules in superfluid helium droplets, in terms of a rotational Lamb shift induced by the many-particle environment. Furthermore, we discover a rich many-body-induced fine structure, emerging in rotational spectra due to a redistribution of angular momentum within the quantum many-body system.
authors.affiliation: ITAMP, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA.|Physics Department, Harvard University, 17 Oxford Street, Cambridge, Massachusetts 02138, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Schmidt
authors.affiliation: IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400 Klosterneuburg, Austria.
authors.forename: Mikhail
authors.initials: M
authors.lastname: Lemeshko