Observation of Majorana Zero Modes in Iron-based Superconductors*

Majorana zero-modes (MZMs) are spatially-localized zero-energy fractional quasiparticles with non-Abelian braiding statistics. They are believed to hold great promise for topological quantum computing. A breakthrough of Majorana zero mode has been achieved in a single material platform of high-T c iron- based superconductor, FeTe 0.55 Se 0.45 , by using scanning tunneling microscopy/spectroscopy (STM/STS) [1]. This material combines the advantages of a simple material, high- T c , and large ratio of Δ/E F . We also revealed the mechanism of two distinct classes of vortices presented in this system, which directly tied with the presence or absence of zero-bias peak [2]. We further found the Majorana conductance plateau in vortices on the iron-based superconductor FeTe 0.55 Se 0.45 [3]. Both the extrinsic instrumental convoluted broadening and the intrinsic quasiparticle poisoning can reduce the conductance plateau value, and when extrinsic instrumental broadening is removed by deconvolution, the plateau is found to nearly reach a 2e 2 /h quantized value. Moreover, we confirmed the existence of MZMs in the vortex cores of CaKFe 4 As 4 and LiFeAs [4,5], single-material superconductors belonging to the iron pnictide family. These results show the great potential of the single-material platforms for Majorana research in the future.

References:

[1] D.F. Wang et al., Science 362, 333 (2018).

[2] L.Y. Kong et al., Nature Physics 15, 1181 (2019).

[3] S.Y. Zhu et al., Science 367, 189 (2020).

[4] W.Y. Liu et al., Nature Commun. 11, 5688 (2020).

[5] L.Y. Kong et al., Nature Commun. 12, 4146 (2021).