Co doped Bi2Se3 topological insulator: a combined theoretical and experimental study

Research on magnetic ion doping in topological insulators like Bi₂Se₃ is gaining prominence rapidly since it has prospective technological implications and also has significant importance in experimental verification of exotic fundamental physical concepts. In this study, we present a comprehensive investigation of Co-doped Bi₂Se₃ by integrating advanced ab initio density functional theory (DFT) calculations with an array of experimental techniques including X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS) and angle-resolved photoemission spectroscopy (ARPES) using synchrotron radiation. This detailed approach goes beyond previous research by not only confirming the long-range crystalline order but also providing a detailed insight into the local atomic environment and electronic structure around Co dopants. Our combined theoretical and experimental investigations undoubtedly reveal that Co atoms preferentially occupy interstitial sites within the van der Waals gap, a result which has provided conclusive clarity regarding the preferred sites for Co doping in Bi₂Se₃. Apart from the above, our theoretical study corroborated by experimental results also explains how Co doping affects magnetic properties of Bi₂Se₃. This enhanced understanding of the interplay between dopant site preference, oxidation state, and resultant magnetic behavior is pivotal for designing next generation topological insulator-based devices with optimized performance.