Sensing Electron Spins of Copper Phthalocyanine via Relaxometry of Shallow Nitrogen-Vacancies in Diamond

Molecular spin systems, particularly electron spin-bearing organic molecules with low spin-orbit coupling, such as copper phthalocyanine (CuPc), have recently emerged as a promising quantum platform. CuPc's electronic spin has demonstrated relatively long coherence times and can be highly customized through chemical modifications, enabling the creation of uniform, stable spin clusters for quantum applications, including quantum sensors and quantum random access memories. Compared to other solid-state spin defect qubits, the current techniques for depositing and fabricating molecular thin films offer greater flexibility and reliability in the manufacturing and usage of these qubits for sensing or interacting with external qubits. <br/>To achieve initialization, detection, and manipulation of single electronic spins in CuPc, single nitrogen-vacancy (NV) centers in diamond serve as excellent tools to characterize quasi-2D samples of CuPc. In this work, $\alpha$-phase CuPc thin layers (&lt;25 nm) were deposited onto the surface of diamond. We demonstrate the interaction between shallow NV centers (depth &lt;10 nm) and CuPc’s electron spin through the relaxometry of NV centers. By demonstrating the interaction between CuPc and NV centers, this work paves the way to exploit this molecule-NV hybrid quantum system for quantum applications.