"In silico" evidence of robust Majorana zero modes in artificial spin chains on superconducting substrates

Abstract We present a first-principles computational approach based on a microscopic relativistic theory of inhomogeneous superconductivity to scrutinize edge states of magnetic chains deposited on the surface of superconductors. Detailed investigations of an iron chain on the top of Au-covered Nb(110) have been carried out with quantitative predictions together with studies of quantities well beyond the reach of experimental capabilities to uniquely identify the topological phase. We confirm that ferromagnetic Fe chains on Au/Nb(110) surface does not support any Majorana Zero Mode (MZM); however, a broad range of spin-spirals can be identified with a robust zero energy state displaying signatures of MZMs. For these spirals, we explore the structure of various superconducting order parameters and the role of spin-orbit coupling. Through additional computational experiments, we provide evidence that MZMs are localized to the boundaries of the topological region of the chain. The robustness of the MZM states is also demonstrated, representing a huge step toward potential experimental realizations.