A correlator product state study of molecular magnetism in the giant Keplerate Mo72Fe30

TL;DR

This study uses the correlator product state tensor network to analyze the magnetic properties of the giant Mo72Fe30 molecule, revealing deviations from traditional models and indicating a phase transition-like change in the ground state.

Contribution

It demonstrates the effectiveness of CPS tensor networks in modeling complex 2D spin systems and provides new insights into the magnetic behavior of the Mo72Fe30 molecule.

Findings

CPS yields better variational energies than DMRG.

Ground state energies follow the rotational band model qualitatively.

Deviations near 1/3 saturation field suggest a phase transition-like change.

Abstract

We have studied the properties of the giant Keplerate molecular magnet Mo72Fe30, as a function of applied magnetic field, using the correlator product state (CPS) tensor network ansatz. The magnet is modeled with an S = 5/2 antiferromagnetic Heisenberg Hamiltonian on the 30-site icosidodecahedron lattice, a model for which exact diagonalization is infeasible. The CPS ansatz produces significant improvements in variational energies relative to previous studies using the density matrix renormalization group, a result of its superior ability to handle strong correlation in two dimensional spin systems. The CPS results reaffirm that the ground state energies adhere qualitatively to the parabolic progression of the rotational band model (RBM), but show important deviations near 1/3 of the saturation field. These deviations predict anomalous behavior in the differential magnetization and heat capacity that cannot be explained by the RBM alone. Finally, we show that these energetic deviations originate from a qualitative change in the ground state that resembles a finite size analogue of a phase transition.