Giant Influence of Clustering and Anti-Clustering of Disordered Surface Roughness on Electronic Tunneling

Abstract

This work reveals the giant influence of spatial distribution of disordered surface roughness on electron tunneling, which is of immediate relevance to the magneto tunnel device and imaging technologies. We calculate the spin-dependent tunneling in Fe/vacuum/Fe junction with disordered surface roughness with the first-principles non-equilibrium dynamical cluster theory. It is found that, at high concentration of surface roughness, different spatial distributions, including the clustered, anti-clustered and completely random roughness characterized by Warren–Cowley parameters, present large deviations from each other in all spin channels. By changing from clustered to anti-clustered roughness, it is surprising that spin polarization of tunneling in parallel configuration (PC) can be drastically reversed from –0.52 to 0.93, while complete randomness almost eliminates the polarization. It is found that the anti-clustered roughness can dramatically quench the tunneling of minority spin in both PC and anti-PC by orders of magnitude, but significantly enhance the transmission of majority spin in PC (by as large as 40%) compared to the results of clustered roughness, presenting distinct influences of differently correlated surface roughness. The spatial correlation of disordered surface roughness can significantly modify the surface resonance of Fe minority spin.