Christian Herschbach

Colossal spin Hall effect in ultrathin metallic films

We predict spin Hall angles up to 80% for ultrathin noble metal films with substitutional Bi impurities. The colossal spin Hall effect is caused by enhancement of the spin Hall conductivity in reduced sample dimension and a strong reduction of the charge conductivity by resonant impurity scattering. These findings can be exploited to create materials with high efficiency of charge to spin current conversion by strain engineering.

Insight into the skew-scattering mechanism of the spin Hall effect: Potential scattering versus spin-orbit scattering

We present a detailed analysis of the skew-scattering contribution to the spin Hall conductivity using an extended version of the resonant scattering model of Fert and Levy [Phys. Rev. Lett. 106, 157208 (2011)]. For 5d impurities in a Cu host, the proposed phase shift model reproduces the corresponding first-principles calculations. Crucial for that agreement is the consideration of two scattering channels related to p and d impurity states since the discussed mechanism is governed by a subtle interplay between the spin-orbit and potential scattering in both angular-momentum channels. It is shown that the potential scattering strength plays a decisive role for the magnitude of the spin Hall conductivity.

Spin Hall effect in two-dimensional systems within the relativistic phase shift model

Recently, a relativistic phase shift model (RPSM) was introduced [D. V. Fedorov et al., Phys. Rev. B 88, 085116 (2013)] to describe the skew-scattering mechanism of the spin Hall effect caused by impurities in bulk crystals. Here, we present its analog derived for two-dimensional (2D) systems. The proposed 2D-RPSM is applied to one-monolayer noble-metal films with various substitutional impurities and the obtained results are compared with those of corresponding first-principles calculations. We demonstrate that, in contrast to the three-dimensional RPSM, the considered model does not provide a sufficient qualitative description of the transport properties. Therefore, an ab initio treatment is necessary for the description of the spin Hall effect in two-dimensional crystals.