Universal optical control of chiral superconductors and Majorana modes

Chiral superconductors are a class of unconventional superconductors that host topologically protected chiral Majorana fermions at interfaces and domain walls 1 – 3 , quasiparticles 4 – 6 that could serve as a platform for topological quantum computing 7 . Here we show that, in analogy to a qubit, the out-of-equilibrium superconducting state in such materials can be described by a Bloch vector and predict that they can be controlled on ultrafast timescales. The all-optical control mechanism is universal, permitting arbitrary rotations of the order parameter, and can induce a dynamical change of handedness of the condensate. It relies on transient breaking of crystal symmetries via choice of pulse polarization to enable arbitrary rotations of the Bloch vector. The mechanism extends to ultrafast timescales and the engineered state persists after the pump is switched off. We predict that these phenomena should appear in graphene 8 – 10 or magic-angle twisted bilayer graphene 11 – 14 , as well as Sr 2 RuO 4 (refs. 15 , 16 ). Furthermore, we show that chiral superconductivity can be detected in time-resolved pump–probe measurements. This paves the way towards a robust mechanism for ultrafast control and measurement of chirally ordered phases and Majorana modes. This study presents a proposal for an all-optical method for manipulating chiral superconductors. Light pulses can switch the handedness of the chirality, potentially enabling controlled local writing of domain walls and associated Majorana modes.