Electrical manipulation of spin states in a single electrostatically gated transition-metal complex

TL;DR

This study demonstrates electrical control over spin states in a single transition-metal complex, enabling reversible high-spin to low-spin transitions via gate voltage, with implications for molecular spintronics.

Contribution

It introduces a method to electrically manipulate spin states in a single molecule, combining experimental spectroscopy with theoretical modeling.

Findings

Gate voltage induces high-spin to low-spin transition.

Spin blockade suppresses tunneling current in low-spin state.

Gate-dependent singlet-triplet splitting observed.

Abstract

We demonstrate an electrically controlled high-spin (S=5/2) to low-spin (S=1/2) transition in a three-terminal device incorporating a single Mn2+ ion coordinated by two terpyridine ligands. By adjusting the gate-voltage we reduce the terpyridine moiety and thereby strengthen the ligand-field on the Mn-atom. Adding a single electron thus stabilizes the low-spin configuration and the corresponding sequential tunnelling current is suppressed by spin-blockade. From low-temperature inelastic cotunneling spectroscopy, we infer the magnetic excitation spectrum of the molecule and uncover also a strongly gate-dependent singlet-triplet splitting on the low-spin side. The measured bias-spectroscopy is shown to be consistent with an exact diagonalization of the Mn-complex, and an interpretation of the data is given in terms of a simplified effective model.