Unusual band order and associated band topology in half-Heusler compound TmPdSb

 In half-Heusler (HH) compounds, apart from metallicity, one can observe insulating, semiconducting, or semi-metallic features. A theoretical study suggests that some of them can have non-trivial topology of electronic structure. Indeed, a precise investigation of the band structure predicted a band inversion in some HH compounds, and in consequence the unusual surface states. Typically, the band structure of HH compounds is very similar either to that of CdTe (topologically trivial) or that of HgTe (topologically nontrivial) and the band inversion at the Γ point manifests topological properties. In our work, we predicted that insulating half-Heusler TmPdSb possesses an indirect band gap and unusual band order. Primarily, based on the exact DFT calculation, we investigated the band structure using the tight-binding model in maximally localized Wannier orbitals basis. We showed that the compound exhibits unusual surface states, with spectra extending over the whole Brillouin zone and independent of the surface terminations. Further analyses show unusual band order at Γ point, which can suggest some relation to the topological half-Heusler. The insulating nature, predicted by the ab initio calculations, is verified from the electronic transport measurements. Linear magnetoresistance (MR) observed at low temperatures and up to a high magnetic field, supported the presence of surface states, both for the magnetic field applied longitudinal and transverse to the current direction. I will also discuss the effect of strain on the band order for that compound.