Observation of two non-thermal fixed points for the same microscopic symmetry

TL;DR

This study demonstrates the existence of two distinct non-thermal fixed points with different universal scaling behaviors in a spinor Bose-Einstein condensate, revealing complex far-from-equilibrium dynamics.

Contribution

It provides experimental evidence of multiple non-thermal fixed points for the same microscopic symmetry in a quantum many-body system.

Findings

Two different initial conditions lead to distinct universal scaling dynamics.

Measurements reveal different phase-amplitude excitations for each fixed point.

The results deepen understanding of universal behavior far from equilibrium.

Abstract

Close to equilibrium, the underlying symmetries of a system determine its possible universal behavior. Far from equilibrium, however, different universal phenomena associated with the existence of multiple non-thermal fixed points can be realized for given microscopic symmetries. Here, we study this phenomenon using a quasi-one-dimensional spinor Bose-Einstein condensate. We prepare two different initial conditions and observe two distinct universal scaling dynamics with different exponents. Measurements of the complex-valued order parameter with spatial resolution allow us to characterize the phase-amplitude excitations for the two scenarios. Our study provides new insights into the phenomenon of universal dynamics far from equilibrium and opens a path towards mapping out the associated basins of non-thermal fixed points.