Nichtgleichgewichtsphänomene in Rydberg-Gittern unter Zwangsbedingungen.

01/07/2020 to 30/06/2023

The exploration of quantum many-body systems far from equilibrium
is a topical subject area in physics. In our project we aim to explore
new aspects of this wide field, and in particular we will explore
quantum analogues of fundamental physical processes underlying
glass forming systems. We build on a recently established connection
between lattice gases of interacting Rydberg atoms – which are
atoms in highly excited states – and the physics of soft-matter models
of glass formers. The latter are spin systems with so-called kinetic
constraints that mimic excluded volume effects in supercooled liquids
and make the relaxation dynamics strongly collective and slow. In
Rydberg gases kinetic constraints emerge naturally as a
consequence of the strong interatomic interactions. The situation we
will focus on in our proposal concerns the so-called facilitation
constraint where the excitation probability is enhanced in the vicinity
of an excited Rydberg atom. This mechanism is akin to canonical
classical glass forming models, such as the Fredrickson-Anderson
spin model, which also features such conditional excitation dynamics,
i.e. a spin is only flipped if a neighbouring spin is excited. These
classical model systems display hallmark features of glassines, such
as dynamical heterogeneity as well as ultra-slow relaxation. Rydberg
atoms offer the unique advantage to extend and explore these
dynamical phenomena in the quantum domain where facilitated spin
flips are fully coherent. Very little is known about this regime, as there
exist hardly any experiments and state-of-the-art numerical
techniques quickly reach their limit of applicability. This is particularly
the case when long times and higher dimensions are involved. The
goal of the proposed project is to conduct an interlinked experiment-
theory research programme that sheds light on the correlated
quantum dynamics of lattice spin gases in the presence of facilitation
constraints. To this end we will augment an existing experimental
platform to allow for the observation and characterisation of Rydberg
lattice gases in one- and two-dimensional systems over long times. Furthermore, we will develop theoretical models and numerical
approaches to understand the correlated many-body dynamics in
close connection to the experiment which will allow us to scrutinise
and validate approximations. We expect that our project will shed new
light on non-equilibrium phenomena, including metastability, ergodicity
breaking as well as the emergence of glassiness, in the largely
unexplored quantum regime. Our research will deliver new
approaches to experimentally control and monitor many-body
quantum systems over long times, we will deliver new theoretical
methods and establish a link between cold atomic physics and the
physics of soft-matter systems.