Observation of conductance plateau of Majorana zero modes in Fe(Te,Se)

Recently, iron-based superconductor turns to be a promising platform for studying Majorana quasiparticles. The sharp and isolated zero-bias conductance peaks (ZBCPs) were observed clearly by high-resolution scanning tunneling microscopy. The wavefucntion behavior of the ZBCPs and the global behavior of vortex bound states series were well studied. It implies that the observed ZBCPs are most probably Majorana zero modes (MZMs), and its topological nature renders the global π-phase shift of vortex bounds states.

There is another long-sought-after fingerprint for MZMs, i.e. 2e2/h-quantized Majorana conductance induced by resonant Andreev reflection. That resonance nature is ensured by the particle-hole equivalence of MZMs and introduces a plateau feature of zero-bias conductance at zero temperature. Due to the large energy level spacing in the vortex core, the iron-based superconductor turns to be a good platform to check that expectation. Here, I will report our recent tunnel-couple tunable STM measurement on a topological vortex of Fe(Te,Se). We find that the conductance of ZBCP has plateau behavior with its value close to or even reach 2e2/h, while other finite energy vortex bound states do not have such exotic behavior.

Ref. Zhu*, Kong*, Cao*, Chen* et al. arXiv: 1904.06124.