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UBC Theses and Dissertations

Unexpected zero bias conductance peak on the topological semimetal Sb(111) with a single broken layer Yam, Yau Chuen


The signature of the long-sought Majorana fermion from a heterostructure of a superconductor and a topological material is the zero bias conductance peak (ZBCP). Topological semimetal Antimony is a good material in making such heterostructure. Since it is of a bilayer crystal structure, it is expected to be cleaved between bilayers. However, we found that on its cleaved surface there can be steps with step heights corresponding to the intrabilayer distance, indicating that there is a broken layer underneath. The dI/dV spectrum observed using scanning tunneling microscope on these abnormal steps are quite different from the usual Sb spectrum and there is a pronounced ZBCP. Using quasiparticle interference imaging, Landau level spectroscopy and density functional theory (DFT), we found that the ZBCP is originated from the changed band structure through van Hove singularity. This shows that when we try to probe the signature of Majorana fermion in the heterostructure, we need to make sure the ZBCP is not from this trivial origin due to the imperfectness of the topological material.

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