Normal state magneto transport properties of FeSe$_{0.5}$Te$_{0.5}$ superconductor: The role of topological surface states

Abstract

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 performed angle-dependent magneto transport measurements on a single crystal of a doped FeCh system, i.e., FeSe$_{0.5}$Te$_{0.5}$. A non-saturating linear magnetoresistance (MR) has been observed under the magnetic field up to 14 T in the normal state of FeSe$_{0.5}$Te$_{0.5}$. The MR is shown to possess anisotropy, which indicates the presence of topological surface states in FeSe$_{0.5}$Te$_{0.5}$. Angle-dependent Magneto-conductivity (MC) at low magnetic fields has been modelled by Hikami Larkin Nagaoka (HLN) formalism, which shows the presence of weak antilocalization (WAL) effect in FeSe$_{0.5}$Te$_{0.5}$. 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 FeSe$_{0.5}$Te$_{0.5}$.