Sign change of the spin Hall effect due to electron correlation in nonmagnetic CuIr alloys

TL;DR

This study demonstrates that local electron correlations in CuIr alloys can reverse the sign of the spin Hall angle, highlighting the importance of electron interactions in spin transport phenomena.

Contribution

It reveals that including electron correlation effects in ab initio calculations can change the predicted sign of the spin Hall angle in CuIr alloys.

Findings

SHA is negative without electron correlation

SHA becomes positive with realistic electron correlation U

Sign of SHA can be controlled by impurity occupation

Abstract

Recently a positive spin Hall angle (SHA) of 0.021, was observed experimentally in nonmagnetic CuIr alloys [Niimi et al., Phys. Rev. Lett. 106, 126601 (2011)] and attributed predominantly to an extrinsic skew scattering mechanism, while a negative SHA was obtained from ab initio calculations [Fedorov et al., Phys. Rev. B 88, 085116 (2013)], using consistent definitions of the SHA. We reconsider the SHA in CuIr alloys, with the effects of the local electron correlation U in 5d orbitals of Ir impurities, included by the quantum Monte Carlo method. We found that the SHA is negative if we ignore such local electron correlation, but becomes positive once U approaches a realistic value. This may open up a way to control the sign of the SHA by manipulating the occupation number of impurities.