A sharp tug on a twisted cord sends a spiral wave along it. Similarly, an ultrashort laser flash in a RhSi crystal gives birth to light instantly twisted into a three-dimensional corkscrew. This is a manifestation of high-harmonic generation: like a powerful pinch makes electrons jump higher and, as they fall back, emit many colors at once — from red to X-rays.

The RhSi crystal itself is already a twisted cord: its atomic lattice is twisted like a screw and can be 'right-handed' or 'left-handed'. This asymmetry gives the emerging light a strictly defined rotation. Inside it, Weyl fermions behave like massless particles, promising electronics based on twisted beams rather than currents.

The idea stems from Charles Townes, the inventor of the laser. Now physicists control the shape of the light wave in attoseconds — a billion times faster than a camera shutter. An unexpected bonus: such a 'light spring' can encode data by the direction of its coils, doubling the information capacity.