Michael Buchhold

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Laser-induced optical excitation of hydrogen-like alkaline and alkalineearth
atoms can be used to create arrays of highly controllable Rydberg
states, which are promising candidates for atom-based quantum
computation and for realizing new many-body phenomena. In a gas of
atoms, the interplay between the laser-drive and strong interactions
between Rydberg states yields new cooperative effects, including either
the complete blocking or the facilitation of excitations by a nearby
Rydberg state. I will discuss theoretical and experimental approaches to
the so-called facilitation regime, in which the creation of excitations is
conditioned on the presence of a nearby Rydberg state. This gives rise to
a kinetically constrained dynamics, supporting the avalanche-like
spreading of excitations and a non-equilibrium phase transition into an
absorbing state with zero excitations. The interplay of interactions, laserdrive,
dissipation and atomic motion, each acting on their individual timescale,
gives rise to a multifaceted dynamics. It ranges from an epidemiclike
spreading of excitations on an emergent complex network at short
times to a long-lived critical regime of repeated scale invariant excitation
avalanches, reminiscent of self-organized criticality, at late times.

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Institute for Theoretical Physics, University of Cologne
Seminar Room 0.03, ETP
Contact: Sebastian Diehl