Unraveling the obscure electronic transition and tuning of Fermi level in Cu substituted Bi₂Te₃ compound

Observation of a broad peak in the temperature (T) dependent resistivity (ρ) in Cu substituted Bi₂Te₃ has been reported earlier, though its origin remains obscured to date. Our investigation reveals that an electronic phase transition accompanied by Fermi level tuning primarily contributes toward the observed $ρ(T)$⁠. The analysis reveals that tuning of the Fermi level affects bulk transport phenomena to produce the unique $ρ(T)$⁠. We have proposed a model to show how the bulk bandgap can affect $ρ(T)$⁠. We have shown that bulk carrier contribution has a greater role in producing such $ρ(T)$⁠, and a detailed discussion supported by temperature dependent ARPES study, Raman study, and XPS study as well as structural study conducted by x-ray diffraction has been presented.