Hidden chiral topological superconductivity in two-dimensional centrosymmetric materials and Majorana mode braiding

By combining $s$-wave superconductivity (SC) and spin-momentum-locked electronic states, topological SC (TSC) can be effectively created. Usually, this requires the candidate systems to be noncentrosymmetric so that there exists some form of antisymmetric, such as Rashba spin-orbit coupling (SOC) effect. In this article, we propose a generic mechanism for inducing chiral TSC of even Chern number in two-dimensional (2D) centrosymmetric materials with hidden spin polarization arising from two noncentrosymmetric layer sectors partnered by inversion symmetry, which enables electrically controllable fusing and braiding of Majorana edge modes. Our model calculations show that the chiral TSC can be achieved with a global SC gap when Zeeman field $Z$, inter-sector interaction ${t}_{\ensuremath{\perp}}$, chemical potential $\ensuremath{\mu}$, and SC pairing potential $\mathrm{\ensuremath{\Delta}}$ satisfy ${Z}^{2}>{({t}_{\ensuremath{\perp}}\ifmmode\pm\else\textpm\fi{}\ensuremath{\mu})}^{2}+{\mathrm{\ensuremath{\Delta}}}^{2}$. Based on first-principles calculations, we further predict 2D bismuth oxyhalides (BiOX, $\mathrm{X}=\mathrm{I}$, Br, Cl, and F) are promising centrosymmetric TSC candidates. In addition to developing a theoretical scheme of chiral TSC in 2D centrosymmetric materials, our findings significantly expend the application of BiOX, whose fabrication techniques are already well-developed, from renewable energy to quantum computing.