Shot noise in diffusive conductors: A quantitative analysis of electron-phonon interaction effects

Using the 'drift-diffusion-Langevin' equation, we have quantitatively analyzed the effects of electron energy relaxation via their interaction with phonons, generally in presence of electron-electron interaction, on shot noise in diffusive conductors. We have found that the noise power $S_I(\omega )$ (both at low and high observation frequencies $\omega$) drops to half of its 'mesoscopic' value only at $\beta \gtrsim 100,$ where $\beta$ is the ratio of the sample length $L$ to the energy relaxation length l_{% {\rm ph}} (the latter may be much larger then the dephasing length). It means in particular that at low temperatures the shot noise may be substantial even when $L\sim 10^{-2}$ -- $10^{-1}$ cm, and the conductor is 'macroscopic' in any other respect.