title: Quantum effects in a weakly frustrated s=1/2 two-dimensional heisenberg antiferromagnet in an applied magnetic field.
abstract: We have studied the two-dimensional S=1/2 square-lattice antiferromagnet Cu(pz)_{2}(ClO4)_{2} (where pz denotes pyrazine), using neutron inelastic scattering and series expansion calculations. We show that the presence of antiferromagnetic next-nearest-neighbor interactions enhances quantum fluctuations associated with resonating valence bonds. Intermediate magnetic fields lead to a selective tuning of resonating valence bonds and a spectacular inversion of the zone-boundary dispersion, providing novel insight into 2D antiferromagnetism in the quantum limit.
authors.affiliation: Laboratory for Solid State Physics, ETH Zurich, CH-8093 Zurich, Switzerland.
authors.forename: N
authors.initials: N
authors.lastname: Tsyrulin
authors.forename: T
authors.initials: T
authors.lastname: Pardini
authors.forename: R R P
authors.initials: RR
authors.lastname: Singh
authors.forename: F
authors.initials: F
authors.lastname: Xiao
authors.forename: P
authors.initials: P
authors.lastname: Link
authors.forename: A
authors.initials: A
authors.lastname: Schneidewind
authors.forename: A
authors.initials: A
authors.lastname: Hiess
authors.forename: C P
authors.initials: CP
authors.lastname: Landee
authors.forename: M M
authors.initials: MM
authors.lastname: Turnbull
authors.forename: M
authors.initials: M
authors.lastname: Kenzelmann