2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/22856We investigate theoretically the ordering effect of quantum spin fluctuations in a Heisenberg antiferromagnet on a two-dimensional network of corner sharing tetrahedra. This network is obtained as a {111} slice of the highly frustrated pyrochlore lattice, from which it inherits the equivalence of all three pairs of opposite bonds of each tetrahedron. The lowest-order (in 1/S) quantum corrections partially lift the huge degeneracy of the classical ground state and select an ensemble of states with long-range valence-bond order.4 pages, 2 EPS figures. Minor revision: clarifications in response to referee comments, additional referencesStrongly Correlated Electronstext