Observation of Scaling of Higher-Order Flow in a Unitary Fermi Gas
Abstract
Collective flow emerging from spatially anisotropic many-body systems is a fundamental manifestation of strongly interacting quantum matter, from ultracold quantum gases to the quark-gluon plasma created in relativistic heavy-ion collisions. Yet how collective flow emerges across different spatial harmonics and how dissipation modifies its evolution remain largely unexplored. Here we investigate the nonequilibrium expansion of a unitary Fermi gas initially confined in nearly homogeneous potentials with engineered angular deformations. By suddenly releasing the confinement, we resolve anisotropic flow harmonics up to the seventh order. Remarkably, after normalization and rescaling by the characteristic expansion timescale, the different harmonics and system sizes exhibit a universal early-time evolution. At longer times, this universality breaks down and we observe an approximately quadratic dependence of the harmonic attenuation on harmonic order, consistent with viscous acoustic scaling. Furthermore, temperature-dependent measurements reveal the role of shear viscosity in the dissipative evolution of higher-order flow. Our results open a new route to exploring the interplay between universal hydrodynamic expansion and dissipative transport, connecting collective dynamics in ultracold quantum gases with anisotropic flow in strongly interacting nuclear matter.
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BibTeX
@misc{yu2026observation,
title = {{Observation of Scaling of Higher-Order Flow in a Unitary Fermi Gas}},
author = {Shuxian Yu and Zhijie Zhang and Yunyi Zhao and Shujin Deng and Meng-Zi Huang and Haibin Wu and Yu-Gang Ma},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.05028},
eprint = {2611.05028},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.05028},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Observation of Scaling of Higher-Order Flow in a Unitary Fermi Gas
AU - Shuxian Yu
AU - Zhijie Zhang
AU - Yunyi Zhao
AU - Shujin Deng
AU - Meng-Zi Huang
AU - Haibin Wu
AU - Yu-Gang Ma
PY - 2026
DA - 2026/11/03
PB - arXiv
DO - 10.48550/arxiv.2611.05028
UR - https://arxiv.org/abs/2611.05028
AB - Collective flow emerging from spatially anisotropic many-body systems is a fundamental manifestation of strongly interacting quantum matter, from ultracold quantum gases to the quark-gluon plasma created in relativistic heavy-ion collisions. Yet how collective flow emerges across different spatial harmonics and how dissipation modifies its evolution remain largely unexplored. Here we investigate the nonequilibrium expansion of a unitary Fermi gas initially confined in nearly homogeneous potentials with engineered angular deformations. By suddenly releasing the confinement, we resolve anisotropic flow harmonics up to the seventh order. Remarkably, after normalization and rescaling by the characteristic expansion timescale, the different harmonics and system sizes exhibit a universal early-time evolution. At longer times, this universality breaks down and we observe an approximately quadratic dependence of the harmonic attenuation on harmonic order, consistent with viscous acoustic scaling. Furthermore, temperature-dependent measurements reveal the role of shear viscosity in the dissipative evolution of higher-order flow. Our results open a new route to exploring the interplay between universal hydrodynamic expansion and dissipative transport, connecting collective dynamics in ultracold quantum gases with anisotropic flow in strongly interacting nuclear matter.
ER -