Quantum phases in frustrated triangular and kagome optical lattices at negative absolute temperatures*

We report on recent experiments investigating the phase diagram of bosons in the triangular and kagome optical lattices. We explore the frustrated physics of these lattices by creating negative absolute temperature states where the sign of the tunneling is effectively inverted. Notably, in this scheme the Hamiltonian remains static and there is no Floquet heating, leading to long lifetimes. In the triangular lattice, we observe that in the frustrated case the critical interaction strength for the bosonic superfluid to Mott insulator transition is strongly reduced, and also observe signatures of the chiral nature of the superfluid as well as indications for a chiral Mott insulator. For the kagome lattice, we investigate the many-body physics that comes into play when we melt a kagome Mott insulator into the flat band.