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Universal optical control of chiral superconductors and Majorana modes

Abstract

Chiral superconductors are a class of unconventional superconductors that host topologically protected chiral Majorana fermions at interfaces and domain walls1,2,3, quasiparticles4,5,6 that could serve as a platform for topological quantum computing7. 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 graphene8,9,10 or magic-angle twisted bilayer graphene11,12,13,14, as well as Sr2RuO4 (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.

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Data availability

All data generated and analysed during this study are available from the corresponding author upon request.

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Journal peer review information: Nature Physics thanks Ivar Martin and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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Acknowledgements

We thank A. Georges and A. J. Millis for helpful discussions. M.C. and M.Z. are supported by the Flatiron Institute, a division of the Simons Foundation. D.M.K. and M.A.S. acknowledge support from the DFG through the Emmy Noether programme (KA 3360/2-1 and SE 2558/2-1, respectively). We acknowledge financial support from the European Union Horizon 2020 research and innovation programme under the European Research Council (ERC Advanced Grant Agreement no. 69409).

Author information

M.C. conceived the idea and performed the time-domain calculations. M.C., D.M.K. and M.A.S. analysed the results. M.Z. performed the density functional theory and dynamical mean-field theory simulations. A.R. supervised the project. All authors contributed to discussions and to the writing of the manuscript.

Competing interests

The authors declare no competing interests.

Correspondence to M. Claassen.

Supplementary information

  1. Supplementary Information

    Supplementary Figs. 1–3, refs. 1–8 and additional mathematical derivations.

  2. Supplementary Video

    Switching of the order parameter Bloch vector represented on the Bloch sphere.

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Fig. 1: Driven chiral superconductors and dynamical symmetry breaking of two-component order parameters.
Fig. 2: Ultrafast control of the chirality of the superconducting order parameter.
Fig. 3: Universal control of chiral superconductors.
Fig. 4: Pump–probe measurement of order parameter dynamics.