Emergent Pauli blocking in a weakly interacting Bose gas

TL;DR

This study reveals that a weakly interacting Bose gas exhibits persistent one-dimensional quantum behavior due to emergent Pauli blocking of transverse excitations, even as it approaches three-dimensional conditions, challenging previous assumptions about dimensional fragility.

Contribution

The paper demonstrates that 1D quantum behavior can extend into the 3D crossover in a Bose gas, attributed to emergent Pauli blocking of transverse excitations, supported by Bethe ansatz analysis.

Findings

1D dephasing dominates relaxation even at high temperatures.

Emergent Pauli blocking causes fermionic statistics in a bosonic system.

1D physics persists beyond traditional limits of one-dimensionality.

Abstract

The relationship between many-body interactions and dimensionality is integral to numerous emergent quantum phenomena. A striking example is the Bose gas, which upon confinement to one dimension (1D) obeys an infinite set of conservation laws, prohibiting thermalization and constraining dynamics. In our experiment, we demonstrate that such 1D behavior can extend much farther into the dimensional crossover towards 3D than expected. Starting from a weakly interacting Bose gas trapped in a highly elongated potential, we perform a quench to instigate dynamics of a single density mode. Employing the theory of Generalized Hydrodynamics, we identify the dominant relaxation mechanism as the 1D dephasing of the relevant collective excitations of the system, the rapidities. Surprisingly, the dephasing remains dominant even for temperatures far exceeding conventional limits of one-dimensionality where thermalization should occur. We attribute our observations to an emergent Pauli blocking of transverse excitations, caused by the rapidities assuming fermionic statistics, despite the gas being purely bosonic. Thus, our study suggests that 1D physics is less fragile than previously thought, as it can persist even in the presence of significant perturbations. More broadly, by employing the exact Bethe ansatz solutions of the many-body system, we facilitate an interpretation of how the emergent macroscopic behavior arises from the microscopic interactions.