Magneto transport and first principle study of strong topological insulator gray Arsenic

In this article, we report the synthesis of a single crystalline gray Arsenic (As) via the Bismuth flux method. The as-grown sample has a Rhombohedral structure as the most stable one. Its XRD (X-ray Diffractometry) pattern ensures a single phase of the grown crystal with space group R-3m. The observed sharp XRD peaks on mechanically exfoliated thin flakes ensured the high crystallinity with growth direction along the c-axis. The EDAX (Energy Dispersive X-ray Analysis) endorses the stoichiometric purity of the as-grown As single crystal. To study the vibrational mode, the Raman spectra are recorded, which show peaks at 196.2 cm-1 and 255.74 cm-1, identified as Eg and A1g modes by DFT calculations. The sample is further characterized by electronic and magneto-transport measurements. The resistivity vs temperature measurement illustrates its metallic nature in the temperature range of 2K to 300K. The measured residual resistivity ratio of the sample is 180, which endorses the high quality of the as-synthesized As single crystal. The RH measurement elucidates huge observed magnetoresistance (MR), along with SdH oscillations, which indicate the presence of topological surface states. The topological nature of As is also confirmed by first principle calculations. Not only orbit projected bands show signatures of band inversion but also the Z2invariant value(1,111) calculated by Wilson loop method affirms As to be a strong topological insulator (TI).