Invited Paper 2D+EM+MI+MN+NS+QS-TuM12
The Observation of Majorana Zero Mode and Conductance Plateau in an Iron-based Superconductor

Tuesday, October 22, 2019, 11:40 am, Room A226

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_0.55Se_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_0.55Se_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_0.55Se_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 2e²/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.

* In collaboration with, D.F. Wang^1,2, L.Y. Kong^1,2, P. Fan^1,2, H. Chen¹, S.Y. Zhu^1,2, W.Y. Liu^1,2, L. Cao^1,2, Y.J. Sun^1,2, S.X. Du^1,2,3, J. Schneeloch⁴, R.D. Zhong⁴, G.D. Gu⁴, Liang Fu⁵, Hong Ding^1,2,3.

¹ Institute of Physics & University of Chinese Academy of Sciences, CAS, Beijing 100190

² CAS Center for Excellence in Topological Quantum Computation, UCAS, Beijing 100190

³ Collaborative Innovation Center of Quantum Matter, Beijing 100190

⁴ Brookhaven National Laboratory, Upton, New York 11973, USA

⁵ Dept. of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

References:

[1] D. F. Wang et al, Science.362, 333 (2008).

[2] L. Y. Kong et al, arXiv:1901.02293 (submitted to Nature Physics on November 19, 2018)

[2] S. Y. Zhu et al, arXiv: 1904.06124 (submitted to Science on February 15, 2019)