Nearest-neighbor resonating valence bonds in YbMgGaO4

TL;DR

This paper demonstrates that YbMgGaO4 exhibits nearest-neighbor resonating valence bond (RVB) excitations, providing the first experimental evidence of such correlations in a quantum spin liquid, revealed through inelastic neutron scattering.

Contribution

The study provides the first experimental observation of nearest-neighbor RVB excitations in YbMgGaO4, linking high-energy spectrum features to RVB physics on a triangular lattice.

Findings

Nearest-neighbor RVB excitations account for most spectral weight above 0.5 meV.

YbMgGaO4 is the first system where nearest-neighbor RVB correlations are observed.

The results connect complex interactions on the triangular lattice to RVB states.

Abstract

Since its proposal by Anderson, resonating valence bonds (RVB) formed by a superposition of fluctuating singlet pairs have been a paradigmatic concept in understanding quantum spin liquids (QSL). Here, we show that excitations related to singlet breaking on nearest-neighbor bonds describe the high-energy part of the excitation spectrum in YbMgGaO4, the effective spin-1/2 frustrated antiferromagnet on the triangular lattice, as originally considered by Anderson. By a thorough single-crystal inelastic neutron scattering (INS) study, we demonstrate that nearest-neighbor RVB excitations account for the bulk of the spectral weight above 0.5 meV. This renders YbMgGaO4 the first experimental system where putative RVB correlations restricted to nearest neighbors are observed, and poses a fundamental question of how complex interactions on the triangular lattice conspire to form this unique many-body state.