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The influence of the electronic Coulomb interaction on the spin-orbit-coupling induced spin Hall effect was discussed. It was shown that the electronic Coulomb interaction may decrease substantially the spin-orbitcoupling induced transverse spin accumulation in a sample when a longitudinal charge current circulates in it, and the decrease of the transverse spin accumulation due to the influences of the Coulomb interaction is determined by the ratio of the spin-drag resistivity to the ordinary resistivity of the sample.The spin Hall effect is a transverse spin accumulation effect induced by the spin-orbit coupling ͑SOC͒ of moving conduction electrons when a longitudinal charge current circulates in a thin slab of nonmagnetic or ferromagnetic metals ͑or semiconductors͒. 1,2 The spin Hall effect is very different from the spin accumulation effect found in magnetic multilayers when a charge current flows in the direction perpendicular to the plane of the layers. 3-6 From theoretical viewpoints, the spin accumulation effect found in magnetic multilayers is caused by the discontinuity of material properties at the interfaces of alternating layers, but the spin Hall effect arises from the SOC induced left-right asymmetric scattering of moving conduction electrons and can occur only in thin slab geometry. The SOC induced left-right asymmetric scattering was known as skew scattering in the literature, and was believed to be the origin of the anomalous Hall coefficients found in ferromagnetic metals. 7,8 In the spin Hall effect, as illustrated in Fig. 1, when a longitudinal charge current flows in a thin slab of paramagnetic or ferromagnetic metals ͑or semiconductors͒, due to the SOC induced leftright asymmetric scattering, spin-up electrons will have a larger probability to be scattered to the right and spin-down electron will have a larger probability to be scattered to the left, leading to transverse nonequilibrium spin accumulation at both sides of the slab. 1,2 It is anticipated that this effect may find some practical applications in the emerging field of spintronics. 1,9,10 For instance, this effect can be applied to generate and/or measure a pure spin current, which carry only spins but carry no charges. 1 In this paper we discuss the influences of the electronic Coulomb interaction on the spin Hall effect. This is an interesting question about the spin Hall effect. Since no charge imbalance occurs in the spin Hall effect, at first sight it seems that the electronic Coulomb interaction should have no substantial influence on the spin Hall effect. However, in this paper we will show that this is not the case. We will show that the electronic Coulomb interaction may have some significant influence on the spin Hall effect. The reason for this is that in the spin Hall effect, due to the spin-orbit coupling of moving conduction electrons, a transverse relative movement will be caused between the spin-up and -down components, but arising from the electronic Coulomb interaction, there will inherently exist a friction betw...

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