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AMO seminar - Mikhail Lemeshko: Rotation of quantum impurities in the presence of a many‐body environment

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torsdag 15. januar 2015,  kl. 15:15 - 16:00


Auditorium I at Chemistry (1514?213)


Henrik Stapelfeldt

Atomic, Molecular, Optical (AMO) physics seminar

Title: Rotation of quantum impurities in the presence of a many?body environment

Speaker: Mikhail Lemeshko, Institute of Science and Technology Austria (IST Austria)


The concepts of rotation and angular momentum are ubiquitous across quantum physics,
whether one deals with the lifetimes of unstable nuclei, accuracy of atomic clocks, or
electronic structure of defect centers in solids. Pioneered by the seminal works of Wigner
and Racah, the quantum theory of angular momentum evolved into a powerful machinery,
commonly used to classify the states of isolated quantum systems and perturbations to their
structure due to electromagnetic or crystalline fields. In “realistic” experiments, however,
quantum systems are almost inevitably coupled to a many?particle environment and a field
of elementary excitations associated with it, which is capable of fundamentally altering the
physics of the system.

We present the first systematic treatment of quantum rotation coupled to a many?particle
environment. By using a series of canonical transformations on a generic microscopic
Hamiltonian, we single out the conserved quantities of the problem. Using a variational
ansatz accounting for an infinite number of many?body excitations, we characterize the
spectrum of angular momentum eigenstates and identify the regions of instability,
accompanied by emission of angular Cerenkov radiation.

The developed technique can be applied to a wide range of systems described by the
angular momentum algebra, from Rydberg atoms immersed into BEC’s, to cold molecules
solvated in helium droplets, to ultracold molecular ions.

NOTE: other location than usual

Henrik Stapelfeldt