The Observation of Majorana Zero Mode and Conductance Plateau in an Iron-based Superconductor

Majorana zero-modes (MZMs) are spatially-localized zero-energy fractional quasiparticles with non-
Abelian braiding statistics that hold great promise for topological quantum computing. Recently, by
using scanning tunneling microscopy/spectroscopy (STM/STS), a new breakthrough of Majorana zero
mode (MZM) was achieved in a single material platform of high-T c iron-based superconductors,
FeTe 0.55 Se 0.45 , which combined advantages of simple material, high- T c , and large ratio of Δ/E F [1]. A
detail STM/STS study of a FeTe 0.55 Se 0.45 single crystal, also revealed the mechanism of two distinct
classes of vortices present in this system, which directly tied with the presence or absence of zero-bias
peak [2]. To further investigated the MZM, it is still needed to find a “smoking-gun” type of evidence
for the existence of MZM, and a quantized conductance plateau is widely believed to be one of them.
Here we report an observation of the Majorana conductance plateau in vortices on the iron
superconductor FeTe 0.55 Se 0.45 surface by using STM/STS [3]. We found that both extrinsic instrumental
convoluted broadening and intrinsic quasiparticle poisoning can reduce the conductance plateau value.
When extrinsic instrumental broadening is removed by deconvolution, the plateau is found to nearly
reach a 2e 2 /h quantized value. The direct observation of a conductance plateau on a single zero-mode in
a vortex strongly supports the existence and protection of MZMs in this iron-based superconductor,
which can serve as a single-material platform for Majorana braiding at relatively high temperature.