Magnetic properties of a capped kagome molecule with 60 quantum spins

TL;DR

This study investigates the quantum magnetic properties of a 60-spin spherical molecule with a capped kagome structure, revealing a degenerate ground state, symmetry breaking, and magnetization plateaus through advanced DMRG techniques.

Contribution

It provides the first detailed quantum analysis of a 60-spin capped kagome molecule, uncovering unique ground state degeneracy and complex magnetic behavior.

Findings

Degenerate ground state breaking spatial symmetry

Magnetization plateaus at 4/5, 3/5, 1/5 of saturation

Zero-point entropy of approximately 5.2 Boltzmann units

Abstract

We compute ground-state properties of the isotropic, antiferromagnetic Heisenberg model on the sodalite cage geometry. This is a 60-spin spherical molecule with 24 vertex-sharing tetrahedra which can be regarded as a molecular analogue of a capped kagome lattice and which has been synthesized with high-spin rare-earth atoms. Here, we focus on the $S=1/2$ case where quantum effects are strongest. We employ the SU(2)-symmetric density-matrix renormalization group (DMRG). We find a threefold degenerate ground state that breaks the spatial symmetry and that splits up the molecule into three large parts which are almost decoupled from each other. This stands in sharp contrast to the behaviour of most known spherical molecules. On a methodological level, the disconnection leads to "glassy dynamics" within the DMRG that cannot be targeted via standard techniques. In the presence of finite magnetic fields, we find broad magnetization plateaus at 4/5, 3/5, and 1/5 of the saturation, which one can understand in terms of localized magnons, singlets, and doublets which are again nearly decoupled from each other. At the saturation field, the zero-point entropy is $S=\ln(182)\approx 5.2$ in units of the Boltzmann constant.