Abstracts Physics

Quantum simulation with an optical kagome lattice

by Max Melchner Von Dydiowa

This thesis reports on the construction and operation of an ultracold atom- based quantum simulator for studying the kagome lattice and the associated flat band. Despite a copious amount of theoretical effort to elucidate the physics of the kagome lattice, experimental kagome physics is still in its infancy. In the case of ultracold atoms, this is mainly due to considerable technical challenges involved in creating an optical kagome lattice, such as the need for active phase stabilization for bichromatic superlattices. We show that we have overcome these challenges and give a thorough account of our machine's technical details. Furthermore, we present calculations and measurements that fully characterise the kagome quantum simulator. Much of the theoretical work on the kagome lattice has focussed on its flat band. Populating flat bands with ultracold atoms has proven to be difficult and it has so far not been possible to prepare flat bands in thermodynamic equilibrium. We show a route towards studying quantum manybody physics in the flat band of the kagome lattice using negative temperatures. In addition we report, for the first time, on the creation of a negative temperature state in a triangular lattice. This thesis additionally serves to collect and consolidate theoretical research that we can directly study with our machine. In particular, we will discuss the properties of bosons in flat bands and their experimental signatures, with the aim of guiding and accelerating the near-term developments and experiments. Finally, we detail our progress towards realizing a quantum gas microscope for the kagome lattice. In this context, we present a new method for super-resolution microscopy of ultracold atoms in optical lattices.