Zero-bias anomaly in asymmetric contacts

The Coulomb electron-electron interaction effect on the tunneling conductan ce of an asymmetric contact consisting of two nonequivalent two-dimensional electron systems, one clean and the other disordered, is considered. It is shown that the zero-bias anomalies typical for symmetric disordered and cl ean contacts are strongly modified in the asymmetric clean-disordered conta ct due to more complicated screening effects and appearance of a new collec tive mode. [S0163-1829(98)04847-4].