Visualization of Topological Boundary Modes Manifesting Topological Nodal-Point Superconductivity

Abstract

The extension of the topological classification of band insulators to topological semimetals gave way to the topology classes of Dirac, Weyl, and nodal line semimetals with their unique Fermi arc and drum head boundary modes. Similarly, there are several suggestions to employ the classification of topological superconductors for topological nodal superconductors with Majorana boundary modes. Here, we show that the surface 1H termination of the transition metal dichalcogenide compound 4Hb-TaS${}_2$, in which 1T-TaS${}_2$ and 1H-TaS${}_2$ layers are interleaved, has the phenomenology of a topological nodal point superconductor. We find in scanning tunneling spectroscopy a residual density of states within the superconducting gap. An exponentially decaying bound mode is imaged within the superconducting gap along the boundaries of the exposed 1H layer characteristic of a gapless Majorana edge mode. The anisotropic nature of the localization length of the edge mode aims towards topological nodal superconductivity. A zero-bias conductance peak is further imaged within fairly isotropic vortex cores. All our observations are accommodated by a theoretical model of a two-dimensional nodal Weyl-like superconducting state, which ensues from inter-orbital Cooper pairing. The observation of an intrinsic topological nodal superconductivity in a layered material will pave the way for further studies of Majorana edge modes and its applications in quantum information processing.

arXiv commentinitial submission

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• Ordered and tunable Majorana-zero-mode lattice in naturally strained LiFeAs
• Magnetic memory and spontaneous vortices in a van der Waals superconductor
• Chiral to Nematic Crossover in the Superconducting State of 4Hb-TaS${}_2$
• Heterogeneous Ta-dichalcogenide bilayer: heavy fermions or doped Mott physics?
• Antiferromagnetism-driven two-dimensional topological nodal-point superconductivity
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• Coexistence of Quasi-two-dimensional Superconductivity and Tunable Kondo Lattice in a van der Waals Superconductor
• Evidence of a two-component order parameter in 4Hb-TaS2 in the Little-Parks effect
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• Nonreciprocal superconductivity
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• Electron delocalization in a 2D Mott insulator
• Charge ordered phases in the hole-doped triangular Mott insulator 4Hb-TaS2
• Topological superconductor candidates PdBi${}_2$Te${}_4$ and PdBi${}_2$Te${}_5$ from a generic ab initio strategy
• A revisit of superconductivity in 4$H_b$-TaS${}_{2-2x}$Se${}_{2x}$ single crystals
• Nonlinear optical responses in multi-orbital topological superconductors
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• Probing the topological character of superconductors via non-local Hanbury-Brown and Twiss correlations
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• Helical Topological Superconducting Pairing at Finite Excitation Energies
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