Spin electric effects in molecular antiferromagnets

TL;DR

This paper develops theoretical tools to identify and analyze molecular antiferromagnets suitable for electric control of spin states, highlighting symmetry considerations, the role of spin-orbit coupling, and experimental signatures.

Contribution

It provides a group-theoretical and Hubbard model analysis of spin-electric coupling mechanisms in molecular magnets, guiding the search for molecules with strong electric control capabilities.

Findings

Spin-electric coupling in triangular molecules is governed by exchange interaction modification.

In pentagonal molecules, spin-electric coupling requires spin-orbit interaction.

Chemical bond properties influence the strength of spin-electric coupling.

Abstract

Molecular nanomagnets show clear signatures of coherent behavior and have a wide variety of effective low-energy spin Hamiltonians suitable for encoding qubits and implementing spin-based quantum information processing. At the nanoscale, the preferred mechanism for control of quantum systems is through application of electric fields, which are strong, can be locally applied, and rapidly switched. In this work, we provide the theoretical tools for the search for single molecule magnets suitable for electric control. By group-theoretical symmetry analysis we find that the spin-electric coupling in triangular molecules is governed by the modification of the exchange interaction, and is possible even in the absence of spin-orbit coupling. In pentagonal molecules the spin-electric coupling can exist only in the presence of spin-orbit interaction. This kind of coupling is allowed for both $s=1/2$ and $s=3/2$ spins at the magnetic centers. Within the Hubbard model, we find a relation between the spin-electric coupling and the properties of the chemical bonds in a molecule, suggesting that the best candidates for strong spin-electric coupling are molecules with nearly degenerate bond orbitals. We also investigate the possible experimental signatures of spin-electric coupling in nuclear magnetic resonance and electron spin resonance spectroscopy, as well as in the thermodynamic measurements of magnetization, electric polarization, and specific heat of the molecules.