---
res:
bibo_abstract:
- Recently it was shown that an impurity exchanging orbital angular momentum with
a surrounding bath can be described in terms of the angulon quasiparticle [Phys.
Rev. Lett. 118, 095301 (2017)]. The angulon consists of a quantum rotor dressed
by a many-particle field of boson excitations, and can be formed out of, for example,
a molecule or a nonspherical atom in superfluid helium, or out of an electron
coupled to lattice phonons or a Bose condensate. Here we develop an approach to
the angulon based on the path-integral formalism, which sets the ground for a
systematic, perturbative treatment of the angulon problem. The resulting perturbation
series can be interpreted in terms of Feynman diagrams, from which, in turn, one
can derive a set of diagrammatic rules. These rules extend the machinery of the
graphical theory of angular momentum - well known from theoretical atomic spectroscopy
- to the case where an environment with an infinite number of degrees of freedom
is present. In particular, we show that each diagram can be interpreted as a 'skeleton',
which enforces angular momentum conservation, dressed by an additional many-body
contribution. This connection between the angulon theory and the graphical theory
of angular momentum is particularly important as it allows to systematically and
substantially simplify the analytical representation of each diagram. In order
to exemplify the technique, we calculate the 1- and 2-loop contributions to the
angulon self-energy, the spectral function, and the quasiparticle weight. The
diagrammatic theory we develop paves the way to investigate next-to-leading order
quantities in a more compact way compared to the variational approaches.@eng
bibo_authorlist:
- foaf_Person:
foaf_givenName: Giacomo
foaf_name: Bighin, Giacomo
foaf_surname: Bighin
foaf_workInfoHomepage: http://www.librecat.org/personId=4CA96FD4-F248-11E8-B48F-1D18A9856A87
- foaf_Person:
foaf_givenName: Mikhail
foaf_name: Lemeshko, Mikhail
foaf_surname: Lemeshko
foaf_workInfoHomepage: http://www.librecat.org/personId=37CB05FA-F248-11E8-B48F-1D18A9856A87
orcid: 0000-0002-6990-7802
bibo_doi: 10.1103/PhysRevB.96.085410
bibo_issue: '8'
bibo_volume: 96
dct_date: 2017^xs_gYear
dct_isPartOf:
- http://id.crossref.org/issn/24699950
dct_language: eng
dct_publisher: American Physical Society@
dct_title: Diagrammatic approach to orbital quantum impurities interacting with
a many-particle environment@
...