Why does the intrinsic spin Hall effect in a Rashba two-dimensional electron gas disappear in the dc limit?

Based on a self-consistent semiclassical approach, in this Letter we try to contribute to the basic physical understanding of some controversial issues about the intrinsic spin Hall effect in a Rashba two-dimensional electron gas. We show that for a Rashba two-dimensional electron gas in the diffusive transport thermodynamic limit, there exist some simple but much clear physical reasons which explain naturally why the intrinsic spin Hall effect in such a system cannot survive in the dc limit. The physical pictures established in this Letter resolve some puzzles existed in some previous theoretical treatments about this extraordinary effect.