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Angulon: physics and applications of a new quasiparticle

Periodic Reporting for period 1 - ANGULON (Angulon: physics and applications of a new quasiparticle)

Reporting period: 2019-02-01 to 2020-07-31

The overarching goal of the project is to develop a theory, describing the physics of rotating „impurities“ such as molecules interacting with a quantum environment, such as a liquid or a crystal. This problem is extremely challenging, since it involves a large number of interacting quantum particles (in principle, on the order of 10^23). Furthermore, in order to describe many physical and chemical processes, one needs to describe time-dynamics, which complicates the problem further.

When developed, the theory will allow to understand and, most important, to control chemical reactions in solvents, which is one of the key problems of chemical physics.
During the first phase of the project, we have achieved a substantial progress in describing the static and dynamical properties of molecules in quantum solvents. Together with the experimental group of Prof. Stapelfeldt (U Aarhus, Denmark), we described the dynamics of small molecules (I2, CS2, OCS) in superfluid helium nanodroplets following a low-intensity laser pulse.

Furthermore, we developed the theory of intermolecular interactions mediated by a quantum solvent, demonstrated the possibility to generate synthetic spin-orbit coupling forces by means of such a solvent and applied parts of the generated knowledge in completely different fields, such as excitonic liquids in semiconductors and chiral organic molecules on surfaces.
Most of the results achieved during the reporting period are beyond the state of the art, since they involve quantum impurities with complex internal structure (such as molecules) immersed in a quantum bath. In addition, a substantial amount of work was concerned with developing time-dependent techniques to describe the dynamics of molecules in solvents, which pushes the limits of the state-of-the-art methods.

By the end of the project we expect to have a reliable theoretical and computational machinery, describing quantum impurities with angular momentum (such as molecules) in various types of environments.
An example of the angulon’s spectral function