An SU(N) Mott insulator of an atomic Fermi gas realized by large-spin Pomeranchuk cooling

TL;DR

This paper reports the realization of an SU(6) symmetric Mott insulator using ytterbium atoms in an optical lattice, demonstrating unique entropy properties and cooling effects relevant for exploring exotic quantum phases.

Contribution

First experimental realization of an SU(6) Mott insulator with ultracold ytterbium atoms in a 3D optical lattice, highlighting entropy and cooling characteristics.

Findings

Observation of Mott insulating phase with suppressed compressibility

Identification of entropy differences between SU(6) and SU(2) systems

Potential for exploring exotic quantum phases at ultra-low temperatures

Abstract

The Hubbard model, containing only the minimum ingredients of nearest neighbor hopping and on-site interaction for correlated electrons, has succeeded in accounting for diverse phenomena observed in solid-state materials. One of the interesting extensions is to enlarge its spin symmetry to SU(N>2), which is closely related to systems with orbital degeneracy. Here we report a successful formation of the SU(6) symmetric Mott insulator state with an atomic Fermi gas of ytterbium (173Yb) in a three-dimensional optical lattice. Besides the suppression of compressibility and the existence of charge excitation gap which characterize a Mott insulating phase, we reveal an important difference between the cases of SU(6) and SU(2) in the achievable temperature as the consequence of different entropy carried by an isolated spin. This is analogous to Pomeranchuk cooling in solid 3He and will be helpful for investigating exotic quantum phases of SU(N) Hubbard system at extremely low temperatures.