Transport evidence of Dirac dispersion in PbBi₂Te₄ 3D topological insulator

The non-trivial nature of the surface states in PbBi_2-xFe_xTe₄ is evident from the observations of the Shubnikov-de Haas (SdH) oscillations with π berry phase. Lower effective mass obtained from the Lifshitz-Kosevich fit and higher mobility values determined from the Dingle analysis confirmed the surface origin of the oscillations. An elongated band outside the surface Fermi surface is identified for pure sample and is absent for doped specimens. Combined SdH oscillations and Hall effect studies reveal the shifting of the Fermi level of PbBi₂Te₄ towards the Dirac point with successive Fe doping. Progressive decrease of the Fermi wave vector (k) and corresponding Fermi energy (E) with Fe doping can be fitted well with straight line, reveals the linear nature of the E-k diagram i.e. Dirac dispersion of topological surface states in PbBi₂Te₄. The observed weak anti-localization corroborates the spin-momentum locking as the consequence of π Berry phase acquires by the spin upon moving round the Dirac point and is consistent with SdH oscillations.