Dissipation through spin Coulomb drag in electronic spin transport and optical excitations

Spin Coulomb drag (SCD) constitutes an intrinsic source of dissipation for spin currents in metals and semiconductors. We discuss the power loss due to SCD in potential spintronics devices and analyze in detail the associated damping of collective spin-density excitations. It is found that SCD contributes substantially to the linewidth of intersubband spin plasmons in semiconductor quantum wells, which suggests the possibility of a purely optical quantitative measurement of the SCD effect in a parabolic well through inelastic light scattering.

Figure 1

Spin transresistivity $\mid \mathrm{Re}{\rho }_{\uparrow \downarrow }\mid$ vs rescaled frequency $\hslash \omega ∕E_F$ for $n={10}^x{\mathrm{cm}}^{-3}$, $x=16,17,18$ as indicated and GaAs parameters ($m=0.067m_e$, $ϵ=12$). Inset: $\mid \mathrm{Re}{\rho }_{\uparrow \downarrow }\mid$ in $\mathrm{m}\Omega \mathrm{cm}$ vs $\hslash \omega$ in eV for the same densities. Dashed line: high-frequency limit Eq. (6).

Figure 2

Upper panel: Spin-plasmon linewidth ${\Gamma }_{\mathrm{SDE}}^{\mathrm{SCD}}$ for a parabolic quantum well versus curvature parameter $\lambda$, for $N_s={10}^{10}$, ${10}^{11}$, and ${10}^{12}{\mathrm{cm}}^{-2}$ and GaAs parameters. The inset illustrates the collective motion of the two spin populations (CDE, in phase; SDE, out of phase). Lower panel: Rescaled linewidth ${\Gamma }_{\mathrm{SDE}}^{\mathrm{SCD}}∕\hslash \omega$.