Normal state magneto transport properties of FeSe_0.5Te_0.5 superconductor: the role of topological surface state

Doped Iron Chalcogenide (FeCh) superconductors are extensively studied in the context of topological superconductivity. However, the evidence of topological surface states in electrical transport measurements of the doped FeCh system is yet warranted. In the present letter, we report the successful growth of the single crystal of FeSe_0.5Te_0.5, with the growth direction along the c-axis confirmed by single crystal X-ray diffraction and High-resolution Transmission electron microscopy (HRTEM). The angle-dependent magneto transport measurements have been performed on a single crystal of doped FeCh system, i.e., FeSe0.5Te0.5. A non-saturating linear magnetoresistance (MR) has been observed under the magnetic field up to ± 14 T (Tesla) in the normal state of FeSe0.5Te0.5. The MR is shown to possess anisotropy, which indicates the presence of topological surface states in FeSe0.5Te0.5. Angle- dependent Magneto conductivity (MC) at low magnetic fields has been modeled by Hikami Larkin Nagaoka (HLN) formalism, which shows the presence of weak antilocalization (WAL) effect in FeSe0.5Te0.5. The observed WAL effect is found to be 2D in nature through angle-dependent magneto transport measurements. Theoretical calculations based on Density Functional Theory (DFT) are also performed to get more confidence on the presence of topological surface states in FeSe0.5Te0.5.