Orbital-driven melting of a bosonic Mott insulator in a shaken optical lattice

TL;DR

This paper explores how resonant periodic forcing in ultracold bosonic atoms in optical lattices can induce an orbital-driven transition from Mott insulator to superfluid, revealing complex phase behavior influenced by kinetic frustration.

Contribution

It demonstrates the realization of a strongly interacting Floquet system with two relevant orbital states and uncovers the conditions for different types of phase transitions.

Findings

Orbital-driven Mott-insulator-to-superfluid transition observed.

Transition type depends on lattice depth and filling.

Kinetic frustration influences the transition nature.

Abstract

In order to study the interplay between localized and dispersive orbital states in a system of ultracold atoms in an optical lattice, we investigate the possibility to coherently couple the lowest two Bloch bands by means of resonant periodic forcing. Considering bosons in one dimension, it is shown that a strongly interacting Floquet system can be realized, where at every lattice site two (and only two) near-degenerate orbital states are relevant. By smoothly tuning both states into resonance we find that the system can undergo an orbital-driven Mott-insulator-to-superfluid transition. As an intriguing consequence of the kinetic frustration in the system, this transition can be either continuous or first-order, depending on parameters such as lattice depth and filling.