Spin relaxation and band excitation of a dipolar BEC in 2D optical lattices

TL;DR

This study investigates dipolar relaxation and band excitation in a 2D optical lattice with chromium atoms, revealing how magnetic fields and tunneling influence interband transitions and metastability.

Contribution

It provides experimental and theoretical analysis of dipolar relaxation rates and demonstrates suppression of relaxation below a magnetic field threshold.

Findings

Interband transitions occur when dipolar relaxation energy matches the lattice band gap.

Dipolar relaxation can be suppressed below a certain magnetic field threshold.

Tunneling in higher lattice bands influences the relaxation process.

Abstract

We observe interband transitions mediated by the dipole-dipole interaction for an array of 1D quantum gases of chromium atoms, trapped in a 2D optical lattice. Interband transitions occur when dipolar relaxation releases an energy which matches or overcomes the lattice band gap. We analyze the role of tunneling in higher lattice bands on this process. We compare the experimental dipolar relaxation rate with a calculation based on a multiple Fermi Golden Rule approach, when the lattice sites are symmetric, and the magnetic field is parallel to the lattice axis. We also show that an almost complete suppression of dipolar relaxation is obtained below a magnetic field threshold set by the depth of the lattice: 1D quantum gases in an excited Zeeman state then become metastable.