Erlangen 2018 – scientific programme
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A: Fachverband Atomphysik
A 16: Atomic Clusters I (joint session A/MO)
A 16.3: Talk
Monday, March 5, 2018, 17:00–17:15, K 2.016
Evidence of angulon quasiparticles formation in superfluid 4He nanodroplets — •Igor Cherepanov, Giacomo Bighin, and Mikhail Lemeshko — IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria
Quasiparticles are a core concept in many-body physics widely used for solving quantum impurity problems [1]. Models based on quasiparticles serve as an alternative to theories implying extensive numerical calculations. Moreover, they provide a more straightforward and intuitive understanding of complex phenomena taking place in many-body systems. Here we present the evidence for the formation of angulon quasiparticles [2] in experiments on trapping molecules in superfluid 4He nanodroplets. The angulon consists of a rotating impurity (such as a molecule) dressed by a field of surrounding bath excitations (phonons, rotons etc.). Anisotropic interactions of the impurity with helium give rise to a number of many-body effects, such as angulon instabilities – resonant transfer of a small amount of angular momentum from the molecule to the superfluid.
We demonstrate that broadening and splitting of spectral lines as well as a violation of rotational selection rules can be explained by means of angulon instabilities [3]. Furthermore, the dynamical emergence of angulon instabilities affects the time evolution of a rotational wavepacket and therefore may be detected in experiments on impulsive molecular alignment in 4He droplets.
M. Lemeshko, Phys. Rev. Lett. 118, 095301 (2017)
R. Schmidt, M. Lemeshko, Phys. Rev. Lett. 114, 203001 (2015)
I. Cherepanov, M. Lemeshko, Phys, Rev. Materials 1, 035602 (2017)