Spin-Electric Control of Individual Molecules on Surfaces

TL;DR

This paper demonstrates a novel spin-electric coupling mechanism in magnetic molecules on surfaces, enabling local, all-electrical control of their spin states for potential quantum computing applications.

Contribution

It introduces a transport-mediated exchange field as a new spin-electric coupling mechanism and demonstrates coherent spin control of molecules using ESR-STM techniques.

Findings

Nonlinear voltage dependence of resonance frequency observed

Transport-mediated exchange field identified as SEC mechanism

All-electrical coherent spin control achieved via Rabi oscillations

Abstract

Individual magnetic molecules are promising building blocks for quantum technologies because of their chemical tunability, nanoscale dimensions, and ability to self-assemble into ordered arrays. However, harnessing their properties in quantum information processing requires precise local control of their spin properties. In this work, we present spin-electric coupling (SEC) for two molecular spin systems, iron phthalocyanine (FePc) and Fe-FePc complexes, adsorbed on a surface. We use electron spin resonance combined with scanning tunnelling microscopy (ESR-STM) to locally address them with the STM tip and electrically tune them using the applied bias voltage. These measurements reveal a pronounced nonlinear voltage dependence of the resonance frequency, linked to the energic onset of other molecular orbitals. We attribute this effect to a transport-mediated exchange field from the magnetic tip, providing a large, highly localized, and broadly applicable SEC mechanism. Finally, we demonstrate that the SEC enables all-electrical coherent spin control: In Rabi oscillation measurements of both single and coupled Fe-FePc complexes we show that the spin dynamics can be tuned, demonstrating a pathway towards electrically controlled quantum operation.