Intrinsic power loss and damping of optical excitations in spintronic devices

Spin Coulomb drag (SCD) provides an intrinsic source of dissipation for spin currents in metals and semiconductors and thus plays a fundamental role in spintronics. We discuss two aspects of SCD and their practical relevance: the power loss in a generic spintronics device, and the damping of collective spin-density excitations in semiconductor quantum wells. A purely optical quantitative measurement of the SCD effect is suggested, and the role of spin–orbit coupling is discussed.