Speaker: Újfalussy Balázs (SZFI)
Title: Zero energy modes of artificial spin chains from first principles
Date: Tuesday, 31 January 2023, 10:00
Place: Building 1, Conference room
Zoom:
https://wigner-hu.zoom.us/j/89227994088?pwd=ZktlVWhTSHZBaGlMUDIwbDhHZ3B…
Meeting ID: 892 2799 4088
Passcode: 626366
Abstract:
Majorana Zero Modes (MZM) at the ends of a chain of magnetic atoms on the surface of a superconductor been of high interest over the past few years triggered by their possible applications as fault tolerant quantum bits. However, experimentally it is still very challenging to uniquely identify MZMs based solely on the spectral properties. In such a situation first-principles calculations are especially helpful, both in identifying and in designing such topological systems.
In this talk 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. We investigate in great detail an iron chain on the top of Au-covered Nb(110) chain and we make quantitative predictions on various properties of the chain based on 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 do not support any 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.
