The $S=1$ dimer system K$_2$Ni(MoO$_4$)$_2$: a candidate for magnon Bose-Einstein condensation

TL;DR

This paper models the magnetic properties of the $S=1$ dimer system K$_2$Ni(MoO$_4$)$_2$ and proposes it as a candidate for magnon Bose-Einstein condensation, supported by first-principles calculations and quantum Monte Carlo simulations.

Contribution

It introduces a detailed effective spin-dimer model for K$_2$Ni(MoO$_4$)$_2$, combining first-principles analysis with numerical simulations to explore its potential for magnetic excitation condensation.

Findings

Model accurately reproduces experimental magnetization data.

Identifies conditions for magnetic excitation condensation.

Discusses potential for supersolid phase under structural distortions.

Abstract

Dimerized quantum magnets provide a unique possibility to investigate Bose-Einstein condensation of magnetic excitations in crystalline systems at low temperature. Here, we model the low-temperature magnetic properties of the recently synthesized spin $S=1$ dimer system K${}_2$Ni(MoO${}_4$)$_2$ and propose it as a new candidate material for triplon and quintuplon condensation. Based on a first principles analysis of its electronic structure, we derive an effective spin-dimer model that we first solve within a mean-field approximation to refine its parameters in comparison to experiment. Finally, the model is solved by employing a numerically exact quantum Monte Carlo technique which leads to magnetic properties in good agreement with experimental magnetization and thermodynamic results. We discuss the emergent spin model of K${}_2$Ni(MoO${}_4$)$_2$ in view of condensation of magnetic excitations in a broad parameter regime. Finally, we comment on a geometrical peculiarity of the proposed model and discuss how it could host a supersolid phase upon structural distortions.