Transport evidence of the spin-polarized topological surface states of alpha-Sn grown on CdTe by molecular beam epitaxy

It is necessary but challenging to verify topological surface states of alpha-Sn by electrical transport. In this work, we demonstrate conclusive transport evidence on topological properties of an alpha-Sn film grown on a CdTe substrate by molecular beam epitaxy. A Berry phase determined from Shubnikov de Haas oscillations is 0.98 pi. A two-dimensional (2D) Fermi surface is clearly demonstrated by angle-dependent oscillations. We believe the nontrivial topology originates from the 2D Dirac fermions of the topological surface states. In addition, both =isotropic magneto-resistance and planar Hall effect have negative amplitudes at higher fields, which we attribute to the spin-flip backscattering in the topological surface states. We also show that these topological surface states have a long relaxation time of similar to 95 fs, making alpha-Sn a potential candidate for high-efficiency spintronics. Published under an exclusive license by AIP Publishing.