Enhancement of Gilbert damping in spin pumping into a two-dimensional electron gas

We theoretically consider spin pumping from a ferromagnetic insulator (FI) into a two-dimensional electron gas (2DEG) in which the Rashba and Dresselhaus spin-orbit interactions coexist. We show that the Gilbert damping of the FI is strongly enhanced when the ratio of the two spin-orbit interactions is near a special value at which the total spin of the 2DEG is conserved. This strong enhancement, which appears only when we take the vertex correction into account, reflects the divergence of the spin relaxation time in the 2DEG. We also show that the shift in the resonant frequency is enhanced in a similar way.Comment: 13 pages, 8 figure