Zero-energy bound states in the high-temperature superconductors at the two-dimensional limit

TL;DR

This study reports the detection of zero-energy bound states in high-temperature superconductors at the two-dimensional limit, resembling Majorana zero modes, using in-situ scanning tunneling spectroscopy, potentially broadening MZM research to more practical temperature regimes.

Contribution

First observation of ZEBSs in high-temperature 2D superconductors at accessible temperatures, suggesting new avenues for topological quantum computing research.

Findings

ZEBSs observed on Fe adatoms in high-Tc superconductors

Spectroscopic features resemble Majorana zero modes

Potential implications for topological quantum computing

Abstract

Majorana zero modes (MZMs) that obey the non-Abelian statistics have been intensively investigated for potential applications in topological quantum computing. The prevailing signals in tunneling experiments "fingerprinting" the existence of MZMs are the zero-energy bound states (ZEBSs). However, nearly all of the previously reported ZEBSs showing signatures of the MZMs are observed in difficult-to-fabricate heterostructures at very low temperatures and additionally require applied magnetic field. Here, by using in-situ scanning tunneling spectroscopy, we detect the ZEBSs upon the interstitial Fe adatoms deposited on two different high-temperature superconducting one-unit-cell-thick iron chalcogenides on SrTiO3(001). The spectroscopic results resemble the phenomenological characteristics of the MZMs inside the vortex cores of topological superconductors. Our experimental findings may extend the MZM explorations in connate topological superconductors towards an applicable temperature regime and down to the two-dimensional limit. While a concrete understanding of the observations is lacking, possible explanations involving novel 2D superconducting states with spin-orbit coupling, spontaneous nucleation of anomalous vortices at the magnetic sites, and noncoplanar magnetic ordering may further stimulate theoretical understandings of the scarcely captured ZEBSs in strongly correlated systems with multiband Cooper pairing.