Ultracold Atoms in a Tunable Optical Kagome Lattice
  Geometrically frustrated systems with a large degeneracy of low energy states are of central interest in condensed-matter physics. The kagome net - a pattern of corner-sharing triangular plaquettes - presents a particularly high degree of frustration, reflected in the non-dispersive orbital bands. The ground state of the kagome quantum antiferromagnet, proposed to be a quantum spin liquid or valence bond solid, remains uncertain despite decades of work. Solid-state kagome magnets suffer from significant magnetic disorder or anisotropy that complicates the interpretation of experimental results. Here, we realize the kagome geometry in a two-dimensional optical superlattice for ultracold $^{87}$Rb atoms. We employ atom optics to characterize the lattice as it is tuned between various geometries, including kagome, one-dimensional stripe, and decorated triangular lattices, allowing for a sensitive control of frustration. The lattices implemented in this work offer a near-ideal realization of a paradigmatic model of many-body quantum physics. 
Gyu-Boong Jo, Jennie Guzman, Claire K. Thomas, Pavan Hosur, Ashvin   Vishwanath, and Dan M. Stamper-Kurn
cond-mat.quant-gas physics.atom-ph quant-ph