Ordered and tunable Majorana-zero-mode lattice in naturally strained LiFeAs

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. By using low-temperature and strong-magnetic-field scanning tunneling microscopy/spectroscopy, a breakthrough of Majorana zero mode has been firstly achieved in a single material platform of high-T_c iron-based superconductor, FeTe_0.55Se_0.45. The mechanism of two distinct classes of vortices presented in this system was revealed, which directly tied with the presence or absence of zero-bias peak. We further found the Majorana conductance plateau in vortices. 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 nearly reaches a 2e²/h quantized value. Moreover, we confirmed the existence of MZMs in the vortex cores of CaKFe₄As₄ and LiFeAs. Based on these works mentioned above, most recently, we have successfully achieved the large-scale, highly-ordered and tunable MZM lattice in strained LiFeAs. Notably, more than 90% of the vortices are topological and possess the characteristics of isolated MZMs at the vortex center, forming ordered MZM lattice with the density and the geometry tunable by external magnetic field.  With decreasing the spacing of neighboring vortices, the MZMs start to couple with each other. This kind of materials combine the advantages of a simple material, high- T_c, large ratio of Δ/E_F and etc.  Our results show a great potential of MZMs in the application of topological quantum computations in the future.

 CO-AUTHORS, G. Li^1,2, D.F. Wang^1,2, S.Y. Zhu^1,2, M. Li^1,2, H. Chen^1,2, P. Fan^1,2, H. Guo^1,2, L. Cao^1,2, Y.Y. Zhang^2,1, L.Y. Kong^1,2, W.Y. Liu^1,2, J. Schneeloch³, R.D. Zhong³, G.D. Gu³, L. Fu⁴, H. Ding^1,2, Z.Q. Wang<sup>5

1</sup> Institute of Physics, Chinese Academy of Sciences, CAS, Beijing 100190, PR China

² School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, PR China

³ Brookhaven National Laboratory, Upton, New York 11973, USA

⁴ Dept. of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

⁵ Department of Physics, Boston College, Chestnut Hill, MA 02467, USA