Well-defined quasiparticles in interacting metallic grains

Spectral functions of mesoscopic systems with large dimensionless conductance were analyzed. It was shown that an important class of spectral functions are dominated by one single state only, which implies the existence of well-defined quasiparticles. The dominance of a single state was found to enable the calculation of zero-temperature spectral functions with high accuracy using the density-matrix renormalization group. The use of the method of calculating spectral functions was also illustrated by evaluating the tunneling density of states.