Scientists observe atomic rotations flipping direction in quantum crystal experiment

The Story

Scientists used ultra-powerful terahertz laser pulses to directly observe angular momentum moving through a crystal lattice for the first time. The experiment revealed an unexpected quantum effect where the direction of atomic rotations reverses as momentum transfers between lattice vibrations. The discovery was published in Nature Physics and led by researchers from the Helmholtz-Zentrum Dresden-Rossendorf and the Fritz Haber Institute of the Max Planck Society.

Key Facts

• The study was led by scientists from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), the Fritz Haber Institute of the Max Planck Society, and collaborators in Berlin, Dresden, Jülich, and Eindhoven.
• The findings were published in Nature Physics.
• Ultra-strong terahertz laser pulses drove one lattice vibration into circular motion, while a second ultrafast laser pulse tracked interactions with another coupled vibration.
• As angular momentum moved from one vibration to another, the direction of rotation flipped.
• The effect comes from the rotational symmetry of the crystal lattice, where certain rotational states are physically equivalent even when spinning in opposite directions.
• The material used was bismuth selenide.
• Angular momenta from lattice vibrations combined to produce a new rotation moving at twice the frequency but in the opposite direction — described as a “1 + 1 = −1” effect.
• This phenomenon resembles an Umklapp process, and is the first experimental demonstration involving lattice angular momentum.
• Researchers say the work may help control ultrafast processes in quantum materials and could contribute to future information technologies and next-generation memory devices.

Conflicting Reports

No conflicting reports identified in the source article.

Still Unclear

No open questions identified in the source article.

Misconceptions

No widespread misconceptions addressed in the source article.

Key Figures

• Olga Minakova, doctoral researcher at the Fritz Haber Institute of the Max Planck Society and central experimental physicist of the study
• Sebastian Maehrlein, head of department at the Institute of Radiation Physics at HZDR, professor at TU Dresden, and leader of the study
• Albert Einstein (historical figure mentioned in background)
• Wander Johannes de Haas (historical figure mentioned in background)

Sources

• https://www.sciencedaily.com/releases/2026/05/260523103903.htm — Primary Source