What will the computers of tomorrow look like? Chances are good that spintronics will play a decisive role in the next generation of computers. In spintronics, the intrinsic angular momentum of an electron (the spin) is used to store, process and transmit data. This technology is already in use today, for example in hard drives. However, the scope of what is possible extends much further: More recent approaches aim at using not just individual spins, but entire spin waves made up of partly hundreds of trillions of spins. Such collective spin excitations are known as magnons. They could enable extremely energy-efficient data transmission – even in the terahertz range.

So far, so good. But how can these spin waves be coupled to today’s technology? "If we develop a concept to perform computer calculations with magnons, it must be compatible with the technology we currently use", says physicist Davide Bossini from the University of Konstanz. "To reach this goal, you have to convert the spin wave into an electrical charge signal". This spin-to-charge conversion is one of the major challenges of spintronics.

The path from spin wave to electrical signal leads through light
In a recent publication in the scientific journal "Nature Communications", a German-Japanese research collaboration led by Davide Bossini shows how such a spin-to-charge conversion can be achieved for spin waves. The physicists make use of an optical effect of magnons in the terahertz range: "Under certain conditions, the magnetic signal of spin waves can be converted into an optical signal", explains Bossini. "We show that magnons can also influence the optical properties of a material. It remains a magnetic signal, but it has measurable optical properties."

Converting the spin wave into an optical signal is the first half of the spin-to-charge conversion process. In the next step, the optical signal can be coupled to electrons, forming the basis for the charge – the electrical signal compatible with today's computer technology.

An extraordinary process with ordinary materials
"You don't need highly specialized signals for our process", says Bossini. "But you need to fulfil certain conditions, and we have now identified these conditions." Bossini's method is based on influencing magnons with laser pulses; his team used wavelengths in the visible and infrared ranges between 400 and 900 nanometres. The exact wavelengths vary depending on the material used, but the principle can easily be transferred to other materials.

Characteristic of Davide Bossini's research team is that they deliberately avoid using exotic materials for their experiments. That the process can be easily implemented in industrial applications and by other research groups is very important to Bossini. He therefore favours standard materials: commercially available lasers and ordinary crystals as material samples. The experiments were conducted at low temperatures of 10 Kelvin (minus 263 degrees Celsius).

Key facts: Original publication: Cimander, M., Wiechert, V., Bär, J. et al. Coherence transfer from optically induced THz magnons to charges. Nat Commun 17, 1480 (2026). Link: https://www.nature.com/articles/s41467-026-69261-y#citeas DOI: https://doi.org/10.1038/s41467-026-69261-y Research project at the University of Konstanz in cooperation with TU Dortmund University and the Institute of Science Tokyo (Japan). Dr Davide Bossini heads an Emmy Noether group at the Department of Physics at the University of Konstanz. His team investigates the interaction between light and solids on ultrafast timescales, in particular the charge and spin dynamics in magnetically ordered materials.