Researchers from RWTH Aachen University, Ioffe Institute and Forschungszentrum Jülich GmbH have shown that the collective motion of spin-polarized electrons can spontaneously generate ultrafast electric currents - without any applied voltage.
In their experiments on strained n-InGaAs semiconductor layers, the team found that when electrons are initialized in the same spin state and exposed to a magnetic field, they produce an alternating current (AC) at gigahertz frequencies. This current persists until the coherent spin precession of the electrons dephases. Its amplitude scales linearly with both the strength of the spin–orbit interaction and the magnetic field, revealing a direct link between spin dynamics and charge motion in solid-state systems.
The researchers describe the effect as a manifestation of a long-predicted quantum phenomenon known as Zitterbewegung - a trembling motion originally proposed for relativistic Dirac electrons. Here, the solid-state analogue emerges from the interference between spin states split by the Zeeman energy. In essence, electron spins set themselves into collective oscillatory motion that electrically drives the crystal lattice.
Beyond its fundamental implications, the discovery opens a new route for ultrafast spin-sensitive electric detection in semiconductors and related materials. The ability to read out spin states via pure spin - orbit-driven currents at GHz frequencies could benefit next-generation spintronic and quantum electronic devices. The findings also suggest pathways to explore similar spin–orbit–driven currents in topological insulators and two-dimensional materials with strong spin - orbit coupling.