Effect of screening on shot noise in diffusive mesoscopic conductors

Shot noise in diffusive mesoscopic conductors, at finite observation frequencies ω (comparable to the reciprocal Thouless time τ⁻¹_T), is analyzed with an account of screening. At low frequencies, the well-known result S_I(ω) = 2eI/3 is is recovered. This result is valid at arbitrary ωτ_T for wide conductors longer than the screening length. However, at least for two very different systems, namely, wide and short conductors, and thin conductors over a close ground plane, noise approaches a different fundamental level, S_I(ω) = eI, at ωτ_T ≫ 1.