Condensation and thermalization of an easy-plane ferromagnet in a spinor Bose gas

A quantum simulation experiment reveals the thermalization of a ferromagnetic system realized with a one-dimensional spinor Bose gas, providing quantitative insights into the condensation dynamics of large magnetic systems. Bose-Einstein condensates are an ideal platform to explore dynamical phenomena emerging in the many-body limit, such as the build-up of long-range coherence, superfluidity or spontaneous symmetry breaking. Here we study the thermalization dynamics of an easy-plane ferromagnet employing a homogeneous one-dimensional spinor Bose gas. We demonstrate the dynamic emergence of effective long-range coherence for the spin field and verify spin-superfluidity by experimentally testing Landau's criterion. We reveal the structure of one massive and two massless emerging modes-a consequence of explicit and spontaneous symmetry breaking, respectively. Our experiments allow us to observe the thermalization of an easy-plane ferromagnetic Bose gas. The relevant momentum-resolved observables are in agreement with a thermal prediction obtained from an underlying microscopic model within the Bogoliubov approximation. Our methods and results are a step towards a quantitative understanding of condensation dynamics in large magnetic spin systems and the study of the role of entanglement and topological excitations for their thermalization.

Automated summary

A quantum simulation experiment using a one-dimensional spinor Bose gas reveals the thermalization of a ferromagnetic system, providing insights into the condensation dynamics of large magnetic systems. The experiment demonstrates the emergence of long-range coherence and spin-superfluidity, and reveals the structure of different modes resulting from explicit and spontaneous symmetry breaking.