A realistic topological p-n junction at the Bi2Se3 (0001) surface based on planar twin boundary defects

We propose a realistic topological p-n junction (TPNJ) by matching two Bi2Se3 (0001) slabs with opposite arrangements of planar twin boundary defects.The atomistic modeling of such a device leads to dislocation defects in the hexagonal lattice in several quintuple layers.Nevertheless,total energy calculations reveal that the interface relaxes,yielding a smooth geometrical transition that preserves the nearest-neighbors fcc-type geometry throughout these defect layers.The electronic,magnetic,and transport properties of the junction have then been calculated at the ab initio level under open boundary conditions,i.e.,employing a thin-film geometry that is infinite along the electron transport direction.Indeed,a p-n junction is obtained with a built-in potential as large as 350 meV.The calculations further reveal the spin texture across the interface with unprecedented detail.As the main result,we obtain non-negligible transmission probabilities around the Γ point,which involve an electron spin-flip process while crossing the interface;