Universal Optical Control of Chiral Superconductors and Majorana Modes

Chiral superconductors are a novel class of unconventional superconductors that host topologically protected chiral Majorana fermions at interfaces and domain walls, with great potential for topological quantum computing. Here we show that the out-of-equilibrium superconducting state in such materials is itself described by a Bloch vector in analogy to a qubit, which can be controlled all-optically on ultrafast time scales [1]. The mechanism is universal and permits a dynamical change of handedness of the condensate, relying on transient dynamical breaking of lattice rotation, mirror or time-reversal symmetries via choice of pump pulse polarization to enable arbitrary rotations of the Bloch vector. The underlying physics can be intuitively understood in terms of transient Floquet dynamics, however the mechanism extends to ultrafast time scales, and importantly the engineered state persists after the pump is switched off. We demonstrate that these novel phenomena should appear in graphene and magic-angle twisted bilayer graphene (TBG), as well as Sr₂RuO₄, as candidate chiral d+id and p+ip superconductors, and show that chiral superconductivity can be detected in time-resolved pump-probe measurements.

[1] M. Claassen, D. Kennes, M. Zingl, M. Sentef, A. Rubio, arXiv:1810.06536 (2018)