Einstein-de Haas effect and induced rotation in an evolving magnetized QCD matter

Abstract

The Einstein-de Haas (EdH) effect describes the emergence of collective rotation driven by spin alignment under an external magnetic field. We investigate this effect in a dynamically expanding quark-gluon plasma (QGP) using a quasiparticle model (QPM). We compute the EdH-induced angular velocity $\omega_{\mathrm{EdH}}$ as a function of temperature, proper time, and fireball radius. Our results show that $\omega_{\mathrm{EdH}}$ grows with proper time and is consequently suppressed at higher temperatures. Near the QGP crossover temperature, $\omega_{\mathrm{EdH}}$ attains a substantial, non-negligible magnitude. We identify a nontrivial crossing between the strong and weak magnetic field regimes that reflects the competition between spin alignment and the energy required to sustain orbital motion. This nontrivial crossing temperature separates a spin-dominated regime from an inertia-dominated regime of magnetic field-induced rotation. These findings establish the EdH effect as a manifestation of angular momentum conservation in magnetized QCD matter.