Nontrivial superconductivity in topological MoTe _{2− x} S _x crystals

Abstract

Topological Weyl semimetals (TWSs) with pairs of Weyl points and topologically protected Fermi arc states have broadened the classification of topological phases and provide superior platform for study of topological superconductivity. Here we report the nontrivial superconductivity and topological features of sulfur-doped -phase MoTe with enhanced T compared with type-II TWS MoTe It is found that -phase S-doped MoTe (MoTe S , ∼ 0.2) is a two-band -wave bulk superconductor (∼0.13 meV and 0.26 meV), where the superconducting behavior can be explained by the pairing model. Further, measurements of the quasi-particle interference (QPI) patterns and a comparison with band-structure calculations reveal the existence of Fermi arcs in MoTe S More interestingly, a relatively large superconducting gap (∼1.7 meV) is detected by scanning tunneling spectroscopy on the sample surface, showing a hint of topological nontrivial superconductivity based on the pairing of Fermi arc surface states. Our work demonstrates that the -phase MoTe S is not only a promising topological superconductor candidate but also a unique material for study of superconductivity.

Two- and Three-Dimensional Superconducting Phases in the Weyl Semimetal TaP at Ambient Pressure

“…For this reason, there is an ongoing effort aimed at achieving superconductivity in such materials and investigating their properties, either through the use of the proximity effect [16,18] or by other means. Successes in this area have been achieved for the type-II Weyl semimetals MoTe 2−x S x [19] and TaIrTe 4 [20], which exhibit intrinsic, exotic superconductivity. For type-I Weyl semimetals, however, such observations are still lacking.…”

Surface superconductivity in the type II Weyl semimetal TaIrTe4

“…Figure 4(c) shows the temperature evolution of dI/dV spectra measured from 0.4 K to 1.10 K. As the temperature increases, the dip at zero bias is reduced and the gap almost vanishes near 1.10 K, which agrees with the onset T c (1.19 K ~ 1.54 K for different samples) obtained from the electrical transport measurements. The BCS ratio 2Δ(0)/k B T c (k B is the Boltzmann constant)) is estimated about 18.4, which is much larger than that of weak coupling BCS superconductors and reminiscent of the possibility of topological superconductivity [13,40,41]. Magnetic field dependence of dI/dV spectra are shown in Fig.…”

“…The chirality of Weyl fermions is responsible for a few novel transport phenomena, such as the chiral anomaly. On the surface of Weyl semimetals, universal signatures of topological Fermi arcs in quasi-particle interference were theoretically predicted [11] and experimentally observed by scanning tunneling microscopy [12,13]. Moreover, the theoretical studies have shown that the presence of superconductivity in Weyl semimetal may lead to a bunch of novel topological phases, including the time-reversal invariant topological superconductor [14], Fulde-Ferrell-Larkin-Ovchinnikov superconductors [15][16][17], and chiral non-Abelian Majorana fermions protected by second Chern numbers [18].…”

“…Quasiparticle interference (QPI) based on spectroscopic-imaging scanning tunneling microscopy, has shown success in identifying the topological surface states of topological insulator [42,43] and topological Fermi arc states of Weyl semimetals TaAs [44], MoTe 2 [12] , [13] and Mo 0.66 W 0.34 Te 2 [45]. (Fig.…”

Phase Transition and Superconductivity Enhancement in Se‐Substituted MoTe2 Thin Films

“…Similarly, chemical pressure is introduced in our case when partial larger Te 2-(2.21 Å) is substituted by Se 2-(1.98 Å)49 . Therefore, the enhancement of T c may be explained by calculating pressure-induced larger superconductivity pairing energy44 . To solidify this assumption, systematic magneto-transport measurements are conducted on pristine T d -MoTe 2 and MoSe x Te 2-x with x=0.95 thin films under a perpendicular filed at different temperatures.…”