Disentangling Pauli blocking of atomic decay from cooperative radiation and atomic motion in a 2D Fermi gas

TL;DR

This paper develops a comprehensive theoretical framework to distinguish Pauli blocking effects from cooperative radiation and atomic motion in a 2D Fermi gas, predicting observable lifetime extensions in degenerate gases and supporting these with experimental data.

Contribution

It introduces a new theoretical model that accounts for quantum statistics, recoil, and cooperative effects simultaneously, enabling clearer identification of Pauli blocking in atomic decay.

Findings

A parameter regime where Pauli blocking extends atomic lifetime by a factor of two.

Experimental observation of decay rate dependence on atom number in strontium atoms.

Theoretical predictions align with experimental measurements in a 2D Fermi gas.

Abstract

The observation of Pauli blocking of atomic spontaneous decay via direct measurements of the atomic population requires the use of long-lived atomic gases where quantum statistics, atom recoil and cooperative radiative processes are all relevant. We develop a theoretical framework capable of simultaneously accounting for all these effects in a regime where prior theoretical approaches based on semi-classical non-interacting or interacting frozen atom approximations fail. We apply it to atoms in a single 2D pancake or arrays of pancakes featuring an effective $\Lambda$ level structure (one excited and two degenerate ground states). We identify a parameter window in which a factor of two extension in the atomic lifetime clearly attributable to Pauli blocking should be experimentally observable in deeply degenerate gases with $\sim 10^{3} $ atoms. Our predictions are supported by observation of a number-dependent excited state decay rate on the ${}^{1}\rm{S_0}-{}^{3}\rm{P_1}$ transition in $^{87}$Sr atoms.