Scientists unlock near-perfect spin currents in overlooked altermagnet

Scientists have achieved a breakthrough in generating nearly 100% pure spin currents in an altermagnet called Cr2SO. Previously, this material was considered unsuitable for such applications. The team, led by Deepika Gill, used a novel optical method to control electron spins without relying on charge flow. The researchers combined infrared light and terahertz radiation to manipulate electron behaviour. By carefully tuning the infrared pulses, they selectively excited electrons in specific energy valleys within the altermagnet. A subsequent terahertz pulse then shifted these electrons, aligning their spins with high precision.

This approach avoids the need for traditional charge movement, which often complicates spin control. Instead, the team exploited a valley selection rule tied to linearly polarised light. The terahertz radiation further refined electron momentum while minimising unwanted spin mixing. The result was a near-perfect spin current—something rarely achieved in altermagnets. The method’s success suggests new possibilities for materials once dismissed as impractical for spintronics.

The findings open doors for ultrafast information processing and broader spintronic applications. Materials like Cr2SO, once overlooked, may now play a key role in future technologies. This all-optical technique offers a cleaner, more efficient way to control spin without charge flow.