Seminar：Skew Scattering from Correlated Systems

Timothy Ziman

Institut Laue Langevinlnstitut Laue Langevin and LPMMC, CNRS, University Grenoble-Alpes, France

 

Time: 14:00pm, Wednesday, Mar. 28, 2018

Location:Room 201, Teaching Building 12, Yuquan Campus, Zhejiang University

 

Abstract

I will discuss the skew scattering mechanisms underlying extrinsic mechanisms for the anomalous and spin Hall effects. First I will recall the phase shift analysis of scattering by single impurities and discuss the difficulty of finding the strong skew effects needed for spintronics.  I will then  examine the enhancement in the effect caused by  resonant skew scattering induced by electron correlations. For single-impurity scattering, local Coulomb correlations may significantly change the observed spin Hall angle. There may be additional  effects because of the special atomic environment close to a surface – extra degeneracies compared to the bulk, enhanced correlations that move the relative d – or  f- levels, and interference effects coming from the lower local dimension. These results may explain the very large spin Hall angle observed in CuBi alloys. I also discuss the impact on the spin Hall effect from cooperative effects, first in  itinerant ferromagnets where there is an anomaly near the Curie temperature originating from high-order spin fluctuations. The second case considered is a metallic spin glass, where  exchange via slowly fluctuating magnetic moments may lead to the precession of an injected spin current. This can decrease the net spin-charge conversion from skew scattering at  low temperatures.