Physical Review B
The American Physical Society
We analyze the spin and charge responses induced in a spin-polarized electron gas by a weak electromagnetic field. The coupled spin-charge response is derived from the equation of motion of the particle distribution function in the presence of the perturbation. To obtain the correct frequency and the wave-vector dependence we introduce the spin-dependent local-field factors, G±σ=Gxσ±Gcσ, which give the exchange (x) and correlation (c) corrections to the random phase approximation. For an arbitrary degree of polarization of the electron gas, we derive the exact analytical expressions for G±σ(q→,ω) in the limit of high frequency or large wave vectors. The results for q→→∞ are expressed in terms of the two-particle correlation function, g(r→) at r=0.
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