Quantum effects in a weakly-frustrated S=1/2 two-dimensional Heisenberg antiferromagnet in an applied magnetic field

TL;DR

This study investigates quantum effects in a 2D S=1/2 antiferromagnet under magnetic fields, revealing how next-nearest neighbor interactions and magnetic tuning influence quantum fluctuations and resonating valence bonds.

Contribution

It demonstrates the impact of antiferromagnetic next-nearest neighbor interactions and magnetic fields on quantum fluctuations and valence bond dynamics in a 2D Heisenberg antiferromagnet.

Findings

Enhanced quantum fluctuations due to next-nearest neighbor interactions.

Magnetic fields induce inversion of zone-boundary dispersion.

Resonating valence bonds are selectively tuned by magnetic fields.

Abstract

We have studied the two-dimensional S=1/2 square-lattice antiferromagnet $Cu(pz)_2(ClO_4)_2$ using inelastic neutron 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.