Universal Optical Control of Chiral Superconductors and Majorana Modes

TL;DR

This paper presents a universal all-optical method to control and detect chiral superconductors and Majorana modes on ultrafast timescales, enabling dynamic manipulation of their topological properties for quantum computing applications.

Contribution

It introduces a novel, universal optical control mechanism for chiral superconductors that allows arbitrary rotations of the order parameter and can induce handedness changes, extending to ultrafast regimes.

Findings

Control of chiral order parameter via ultrafast optical pulses.

Detection of chiral superconductivity through pump-probe measurements.

Potential application to graphene, TBG, and Sr$_2$RuO$_4$.

Abstract

Chiral superconductors are a novel class of unconventional superconductors that host topologically protected chiral Majorana fermions at interfaces and domain walls, elusive quasiparticles that could serve as a platform for topological quantum computing. 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 controlled on ultrafast time scales. 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 time scales, and importantly the engineered state persists after the pump is switched off. We demonstrate that these phenomena should appear in graphene or magic-angle twisted bilayer graphene (TBG), as well as Sr$_2$RuO$_4$, as candidate chiral $d+id$ and $p+ip$ superconductors, respectively. 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.