Pinwheel valence-bond solid and triplet excitations in the two-dimensional deformed kagome lattice

Abstract

Determining ground states of correlated electron systems is fundamental to understanding unusual phenomena in condensed-matter physics. A difficulty, however, arises in a geometrically frustrated system in which the incompatibility between the global topology of an underlying lattice and local spin interactions gives rise to macroscopically degenerate ground states1, potentially prompting the emergence of quantum spin states, such as resonating valence bond2-7and valence-bond solid8-11(VBS). Although theoretically proposed to exist in a kagome lattice-one of the most highly frustrated lattices in two dimensions being comprised of corner-sharing triangles-such quantum-fluctuation-induced states have not been observed experimentally. Here we report the first realization of the 'pinwheel' VBS ground state in the S=1/2 deformed kagome lattice antiferromagnet Rb2Cu3SnF12(refs 12, 13). In this system, a lattice distortion breaks the translational symmetry of the ideal kagome lattice and stabilizes the VBS state. © 2010 Macmillan Publishers Limited. All rights reserved.