Nearly quantized conductance plateau of vortex zero mode in an iron-based superconductor

Abstract

Majorana zero modes (MZMs) are spatially-localized zero-energy fractional quasiparticles with non-Abelian braiding statistics that hold promise for topological quantum computing. Owing to the particle-antiparticle equivalence, MZMs exhibit quantized conductance at low temperature. By utilizing variable-tunnel-coupled scanning tunneling spectroscopy, we study tunneling conductance of vortex bound states on FeTe0.55Se0.45 superconductors. We report observations of conductance plateaus as a function of tunnel coupling for zero-energy vortex bound states with values close to or even reaching the 2e2/h quantum conductance (here e is the electron charge and h is Planck’s constant). In contrast, no plateaus were observed on either finite energy vortex bound states or in the continuum of electronic states outside the superconducting gap. This behavior of the zero-mode conductance supports the existence of MZMs in FeTe0.55Se0.45.

On the Remarkable Superconductivity of FeSe and Its Close Cousins

“…[409]. (e) Same as (d) but for FeTe 0.55 Se 0.45 [412]. (f) Color-scale plot of the same data as in (e) (upper panel), and a line-cut at zero bias versus G N (lower panel), reaching a plateau near 2e 2 /h.…”

“…A clear prediction of proximitized topological surface states is the emergence of MZMs inside the cores of field-induced vortex lines [384]. A number of experimental groups have performed detailed STM experiments on the surfaces of FeTe 0.55 Se 0.45 and (Li 0.84 Fe 0.16 )OHFeSe and discussed the possibility of MZMs in the data [399,[406][407][408][409][410][411][412]. The topic is complicated, e.g., due to the sensitivity to instrumental resolution, unknown effects of impurity pinning sites [352], contributions from bulk states, quasi-particle poisoning, sample inhomogeneity, disordered vortex lattices, and the presence of other topologically trivial but contaminating low-energy vortex cores states.…”

“…Most vortices in FeTe 0.55 Se 0.45 do not reach plateaus at 2e 2 /h, possibly due to thermal smearing or other non-ideal (unresolved) effects. From [412]. Reprinted with permission from AAAS.…”

Electronic and magnetic characterization of epitaxial VSe2 monolayers on superconducting NbSe2

“…It is currently attracting intense attention due to its potential role in building blocks for Majorana-based qubits for topological quantum computation [12][13][14] . While there are very few potential real materials exhibiting topological superconductivity [15][16][17][18] , in a designer material the desired physics emerges from the engineered interactions between the different components. For topological superconductivity, one needs to combine s-wave superconductivity with magnetism and spin-orbit coupling to create an artificial topological superconductor 12,19 .…”

Non-unitary superconductivity in the monolayer of orthorhombic CoSb

“…Among of them, the prominent chiral pairing superconductors originated from the contribution of orbital angular momentum of Cooper paired electrons, such as the chiral p-wave pairing topological superconductors 1,2 , have received great attentions as they host the Majorana quasiparticles at the boundaries [3][4][5][6][7][8] , which is equivalent to the non-Abelian Moore-Read (Pfaffian) spintriplet paired state in the fractional quantum Hall effect with filling factor of 5/2 [9][10][11] , and has potential applications in the topological quantum computing [12][13][14][15][16][17] . Experimentally, the evidences of observing Majorana bound states have been extensively reported in various quantum systems, including the one-dimensional nanowires in contact with superconductors [18][19][20][21][22] , at the edges of iron-atoms chains formed on the surface of superconducting lead 23 , at the interface between a topological insulator and an s-wave superconductor 24,25 , and the quantum spin liquids 26 , as well as the iron-based superconductors [27][28][29][30][31][32][33] .…”