Electric field control of spins in molecular magnets
Physical Review Letters American Physical Society
Abstract:
Coherent control of individual molecular spins in nano-devices is a pivotal prerequisite for fulfilling the potential promised by molecular spintronics. By applying electric field pulses during time-resolved electron spin resonance measurements, we measure the sensitivity of the spin in several antiferromagnetic molecular nanomagnets to external electric fields. We find a linear electric field dependence of the spin states in Cr$_7$Mn, an antiferromagnetic ring with a ground-state spin of $S=1$, and in a frustrated Cu$_3$ triangle, both with coefficients of about $2~\mathrm{rad}\, \mathrm{s}^{-1} / \mathrm{V} \mathrm{m}^{-1}$. Conversely, the antiferromagnetic ring Cr$_7$Ni, isomorphic with Cr$_7$Mn but with $S=1/2$, does not exhibit a detectable effect. We propose that the spin-electric field coupling may be used for selectively controlling individual molecules embedded in nanodevices.Experimental Realisation of Multi-Qubit Gates Using Electron Paramagnetic Resonance
Tailoring the electronic configurations of YPc2 on Cu(111): decoupling strategies for molecular spin qubit platforms
Nanoscale, 2025,17, 22163-22173
Abstract:
Molecule-based spin architectures have been proposed as promising platforms for quantum computing. Among the potential spin qubit candidates, yttrium phthalocyanine double-decker (YPc2) features a diamagnetic metal ion core that stabilizes the molecular structure, while its magnetic properties arise primarily from an unpaired electron (S = 1/2) delocalized over the two phthalocyanine (Pc) ligands. Understanding its properties in the proximity of metal electrodes is crucial to assess its potential use in molecular spin qubit architectures. Here, we investigated the morphology and electronic structure of this molecule adsorbed on a Cu(111) surface using scanning tunneling microscopy (STM). On Cu(111), YPc2 adsorbs flat, with isolated molecules showing a preferred orientation along the 〈111〉 crystal axes. Moreover, we observed two different types of self-assembly patterns when growing molecular patches. For YPc2 in direct contact with Cu(111), STM revealed widely separated highest occupied and lowest unoccupied molecular orbitals (HOMO/LUMO), suggesting the quenching of the unpaired spin. Conversely, when YPc2 is separated from the metal substrate by a few-layer thick diamagnetic zinc phthalocyanine (ZnPc) layer, we found the HOMO to split into singly occupied and singly unoccupied molecular orbitals (SOMO/SUMO). We observed that more than 2 layers of ZnPc are needed to avoid intermixing between the two molecules and spin quenching in YPc2. Density functional theory (DFT) calculations reveal that spin quenching is due to the hybridization between YPc2 and Cu(111) states, confirming the importance of using suitable decoupling layers to preserve the unpaired molecular spin. Our results suggest the potential of YPc2/ZnPc heterostructures as a stable and effective molecular spin qubit platform and validate the possibility of integrating this molecular spin qubit candidate in future quantum logic devices.