Researchers led by Xuefeng Guo of Peking University and Chuancheng Jia of Nankai University, together with Mingliang Li of the University of Hong Kong and Beijing Institute of Technology, have published a comprehensive review outlining how individual molecules can be used to encode, manipulate and detect electron spin, laying out a roadmap toward ultra-compact, low-power spintronic and molecular-scale quantum information devices.
Image from: Nano Research
The review surveys the molecular building blocks that make single-molecule spintronics possible - single-molecule magnets, spin-crossover complexes, organic radicals and chiral molecules - each offering a different route to control spin at the single-molecule level, from the large magnetic anisotropy and slow relaxation of single-molecule magnets to the switchable spin selectivity chiral molecules generate without any magnetic field via the chiral-induced spin selectivity effect. Measurement techniques such as spin-polarized scanning tunneling microscopy and electron spin resonance, combined with gated molecular junctions, have let researchers observe and manipulate spin transport, coherence and many-body effects such as the Kondo effect directly at the single-molecule scale.
Drawing on this body of work, the authors catalog functional device prototypes already demonstrated in single-molecule junctions: spin valves reaching magnetoresistance ratios above 1800%, spin switches that operate at room temperature, and molecular spin qubits with coherence times in the microsecond range. "Single-molecule spintronics represents a paradigm shift in how we think about information processing," said Guo. "By encoding, manipulating, and detecting electron spin at the level of individual molecules, we can potentially overcome the limitations of conventional electronics and create devices that are not only smaller but also far more energy-efficient."
The review also addresses reproducibility, one of the field's central obstacles: variations in binding geometry, local electrostatic environment and molecule-electrode coupling can cause significant fluctuations in spin readout. The authors recommend large-scale statistical measurements, standardized reference molecules, and two-dimensional electrodes with van der Waals gaps to improve interface quality, alongside isotopic purification and engineered clock transitions to extend coherence times for quantum applications. "By correlating molecular design with quantum transport mechanisms, we can create a comprehensive roadmap for developing practical devices," said Jia. Li added that continued advances in molecular design, interfacial engineering and quantum-coherent control could let single-molecule spin devices "evolve from precision testbeds into functional building blocks for low-power spin logic and chemically defined quantum technologies."