STRONG ELECTRON-TUNNELING THROUGH MESOSCOPIC METALLIC GRAINS

We describe electron transport through small metallic grains with Coul omb blockade effects beyond the perturbative regime. For this purpose we study the real-time evolution of the reduced density matrix of the system. In the first part of the paper we present a diagrammatic expan sion for not too high junction conductance, h/4 pi(2)e(2)R(t) less tha n or similar to 1, in a basis of charge states. Quantum fluctuations r enormalize system parameters and lead to finite lifetime broadening in the gate-voltage-dependent differential conductance. We derive analyt ic results for the spectral density and the conductance in the limit w here only two charge states play a role. In the second part of the pap er we consider junctions with large conductance, h/4e(2)R(t) greater t han or similar to 1. In this case contributions from all charge states , which broaden and overlap, become important. We analyze the problem in a quasiclassical approximation. The two complementary approaches co ver the essential features of electron tunneling for all parameters. [ S0163-1829(97)01948-6].