Spin gradient thermometry for ultracold atoms in optical lattices

TL;DR

This paper introduces spin gradient thermometry, a novel technique for measuring ultracold atom temperatures in optical lattices, effective across various regimes including the Mott insulator phase, demonstrated with rubidium atoms.

Contribution

The paper presents a new thermometry method based on spin separation and transition layer measurement, applicable over a broad range of lattice depths and temperatures.

Findings

Effective temperature measurement in the Mott insulator regime

Lowest measured temperature of 1 nK achieved

Potential for exploring spin physics in ultracold systems

Abstract

We demonstrate spin gradient thermometry, a new general method of measuring the temperature of ultracold atoms in optical lattices. We realize a mixture of spins separated by a magnetic field gradient. Measurement of the width of the transition layer between the two spin domains serves as a new method of thermometry which is observed to work over a broad range of lattice depths and temperatures, including in the Mott insulator regime. We demonstrate the thermometry in a system of ultracold rubidium atoms, and suggest that interesting spin physics can be realized in this system. The lowest measured temperature is 1 nK, indicating that the system has reached the quantum regime, where insulating shells are separated by superfluid layers.