Two-dimensional topological superconductivity in Pb/Co/Si(111)

TL;DR

This paper reports the experimental observation of dispersive in-gap states at the edges of 2D topological superconducting domains created by a Pb monolayer on Co/Si(111), revealing propagating Majorana edge states and topological phase transitions.

Contribution

It provides the first direct evidence of dispersive edge states in 2D topological superconductors and demonstrates control of topological phases via magnetic domain magnetization.

Findings

Observation of dispersive in-gap states around superconducting domains.

Identification of chiral and residual helical edge modes.

Potential for engineering quantum phases through magnetic control.

Abstract

Just like insulators can host topological Dirac states at their edges, superconductors can also exhibit topological phases characterized by Majorana edge states. Remarkable zero-energy states have been recently observed at the two ends of proximity induced superconducting wires, and were interpreted as localized Majorana end states in one-dimensional (1D) topological superconductor. By contrast, propagating Majorana states should exist at the 1D edges of two-dimensional (2D) topological superconductors. Here we report the direct observation of dispersive in-gap states surrounding topological superconducting domains made of a single atomic layer of Pb covering magnetic islands of Co/Si(111). We interpret the observed continuous dispersion across the superconducting gap in terms of a spatial topological transition accompanied by a chiral edge mode and residual gaped helical edge states. Our experimental approach enables the engineering and control of a large variety of novel quantum phases. This opens new horizons in the field of quantum materials and quantum electronics where the magnetization of the domains could be used as a control parameter for the manipulation of topological states.