Fermionic Mott Insulators, Band Insulators, and Metals under the Quantum Gas Microscope

Philipp M. Preiss, Jonathan Simon, Waseem Bakr +3 more

Daniel Greif, Maxwell F. Parsons, Anton Mazurenko +5 more

The complexity of quantum many-body systems originates from the interplay of strong interactions, quantum statistics, and the large number of quantum-mechanical degrees of freedom. Probing these systems on a microscopic level with single-site resolution offers important insights. Here we report site-resolved imaging of two-component fermionic Mott insulators, metals, and band insulators, using ultracold atoms in a square lattice. For strong repulsive interactions, we observed two-dimensional Mott insulators containing over 400 atoms. For intermediate interactions, we observed a coexistence of phases. From comparison to theory, we find trap-averaged entropies per particle of 1.0 times the Boltzmann constant (k(B)). In the band insulator, we find local entropies as low as 0.5 k(B). Access to local observables will aid the understanding of fermionic many-body systems in regimes inaccessible by modern theoretical methods.

Robert Jördens

Jirayu Mongkolkiattichai, Liyu Liu, Davis Garwood +2 more

The authors probe fermionic Mott insulators in a geometrically frustrated symmetric triangular lattice using a quantum gas microscope with single-site resolution. They demonstrate the detection of antiferromagnetic spin-spin correlations and perform thermometry by comparison to numerical calculations.

J. Jaramillo, Sebastian Greschner, T. Vekua

Under the influence of an external magnetic field and spin-changing collisions, the band insulator state of one-dimensional $s$-wave repulsively interacting four-component fermions at half-filling transforms into Mott insulator states with a spontaneously doubled unit cell: a dimerized state for shallow lattices and a N\'eel state for deep lattices via an intermediate topological state. These Mott insulator phases could be of special interest for experiments as they can be reached starting from band insulator state and changing magnetic field adiabatically.

Melih Okan, Lawrence W. Cheuk, Matthew A. Nichols +3 more