Dark-state sideband cooling in an atomic ensemble

TL;DR

This paper demonstrates a dark-state sideband cooling technique in an atomic ensemble that achieves subrecoil temperatures, enabling preparation of atoms in their vibrational ground state for advanced ultracold physics experiments.

Contribution

It introduces a simple, effective dark-state sideband cooling method for large atomic ensembles, achieving near-zero vibrational quantum states in a harmonic potential.

Findings

Achieved 100 nK temperature in 85Rb atoms

Demonstrated suppression of carrier transition across vibrational states

Potential for generalization to other atomic and molecular species

Abstract

We utilize the dark state in a {\Lambda}-type three-level system to cool an ensemble of 85Rb atoms in an optical lattice [Morigi et al., Phys. Rev. Lett. 85, 4458 (2000)]. The common suppression of the carrier transition of atoms with different vibrational frequencies allows them to reach a subrecoil temperature of 100 nK after being released from the optical lattice. A nearly zero vibrational quantum number is determined from the time-of-flight measurements and adiabatic expansion process. The features of sideband cooling are examined in various parameter spaces. Our results show that dark-state sideband cooling is a simple and compelling method for preparing a large ensemble of atoms into their vibrational ground state of a harmonic potential and can be generalized to different species of atoms and molecules for studying ultracold physics that demands recoil temperature and below.