Field-Tuned Quantum Effects in a Triangular-Lattice Ising Magnet

TL;DR

This study investigates quantum effects in a triangular-lattice Ising magnet, revealing a quasi-plateau state and unconventional magnetic behaviors driven by quantum fluctuations and frustration, supported by experimental and theoretical analysis.

Contribution

It provides the first detailed experimental and theoretical characterization of quantum fluctuation effects in TmMgGaO4 under magnetic fields.

Findings

Discovery of a quasi-plateau state induced by quantum fluctuations

Unconventional non-monotonic field and temperature dependence of magnetic properties

Observation of coherent magnon-like excitations in high field regime

Abstract

We report thermodynamic and neutron scattering measurements of the triangular-lattice quantum Ising magnet TmMgGaO 4 in longitudinal magnetic fields. Our experiments reveal a quasi-plateau state induced by quantum fluctuations. This state exhibits an unconventional non-monotonic field and temperature dependence of the magnetic order and excitation gap. In the high field regime where the quantum fluctuations are largely suppressed, we observed a disordered state with coherent magnon-like excitations despite the suppression of the spin excitation intensity. Through detailed semi-classical calculations, we are able to understand these behaviors quantitatively from the subtle competition between quantum fluctuations and frustrated Ising interactions.