Template-directed 2D nanopatterning of S = 1/2 molecular spins

January 26, 2023

Kyungju Noh, Luciano Colazzo, Corina Urdaniz, Jaehyun Lee, Denis Krylov, Parul Devi, Andrin Doll, Andreas J. Heinrich, Christoph Wolf, Fabio Donati and Yujeong Bae

Nanoscale Horizons (2023)


In quantum information processing, molecular qubits are emerging as a new platform for qubit, because the self-assembly properties of molecules can be used to construct quantum architectures with a large number of molecules in atomic precision. In a quantum architecture composed of molecules, the interaction between quantum spins can be controlled by adjusting the distance between molecules, which is particularly important for use as a quantum device. In this study, we used TiOPc, having an identical structure with VOPc molecule, as a template layer, to decouple and align VOPc molecules with electron spin 1/2 on the surface. In addition, the orbital structure of VOPc single molecules was revealed through a scanning tunnel microscope, and the generation mechanism of molecular arrangement was revealed by density functional theory simulations. The charge on the metal substrate shifts to the molecular template, gives strain on the molecular template, creating minimum distance between VOPc molecules without changing the electron spin properties of it. These results create a basis for subsequent grafting of molecular quantum bits into solid-based quantum devices.


Molecular spins are emerging platforms for quantum information processing. By chemically tuning their molecular structure, it is possible to prepare a robust environment for electron spins and drive the assembly of a large number of qubits in atomically precise spin-architectures. The main challenges in the integration of molecular qubits into solid-state devices are (i) minimizing the interaction with the supporting substrate to suppress quantum decoherence and (ii) controlling the spatial distribution of the spins at the nanometer scale to tailor the coupling among qubits. Herein, we provide a nanofabrication method for the realization of a 2D patterned array of individually addressable Vanadyl Phthalocyanine (VOPc) spin qubits. The molecular nanoarchitecture is crafted on top of a diamagnetic monolayer of Titanyl Phthalocyanine (TiOPc) that electronically decouples the electronic spin of VOPc from the underlying Ag(100) substrate. The isostructural TiOPc interlayer also serves as a template to regulate the spacing between VOPc spin qubits on a scale of a few nanometers, as demonstrated using scanning tunneling microscopy, X-ray circular dichroism, and density functional theory. The long-range molecular ordering is due to a combination of charge transfer from the metallic substrate and strain in the TiOPc interlayer, which is attained without altering the pristine VOPc spin characteristics. Our results pave a viable route towards the future integration of molecular spin qubits into solid-state devices.