Bidirectional dynamic scaling in an isolated Bose gas far from
equilibrium
Nature Physics Nature Research
Authors:
Jake AP Glidden, Christoph Eigen, Lena H Dogra, Timon A Hilker, Robert P Smith, Zoran Hadzibabic
Abstract:
Understanding and classifying nonequilibrium many-body phenomena, analogous
to the classification of equilibrium states of matter into universality
classes, is an outstanding problem in physics. Any many-body system, from
stellar matter to financial markets, can be out of equilibrium in a myriad of
ways; since many are also difficult to experiment on, it is a major goal to
establish universal principles that apply to different phenomena and physical
systems. At the heart of the classification of equilibrium states is the
universality seen in the self-similar spatial scaling of systems close to phase
transitions. Recent theoretical work, and first experimental evidence, suggest
that isolated many-body systems far from equilibrium generically exhibit
dynamic (spatiotemporal) self-similar scaling, akin to turbulent cascades and
the Family-Vicsek scaling in classical surface growth. Here we observe
bidirectional dynamic scaling in an isolated quench-cooled atomic Bose gas; as
the gas thermalises and undergoes Bose-Einstein condensation, it shows
self-similar net flows of particles towards the infrared (smaller momenta) and
energy towards the ultraviolet (smaller lengthscales). For both infrared (IR)
and ultraviolet (UV) dynamics we find that the scaling exponents are
independent of the strength of the interparticle interactions that drive the
thermalisation.
