Coulomb breach effect emerging in shot noise

Noise can be a unique probe of electron-electron correlations in nanoscale electron devices. While stationary or small signal transport can often be s imply understood in terms of single particle behaviour, noise can be extrem ely sensitive to many-body effects (Landauer L 1996 Physica B 227 156). We present a new collective phenomenon emerging in electron transport in a resonant tunnelling diode, due to Coulomb repulsion dramatically magnified by the particular shape of the density of states in the quantum well. This phenomenon, for which the name of Coulomb breach is proposed, reveals itsel f by making shot noise several times greater than that expected in the abse nce of correlated electron motion. Experimental results showing shot noise enhancement of a factor 6.6 are reported.