QUASI-PARTICLE LIFETIME IN A QUANTUM-DOT

The quasi-particle lifetime is calculated for electrons in a quantum dot as a function of energy, disorder, and dot size. As a result of electron-electron interaction, the spectrum is discrete only in close vicinity of the Fermi level. In the strongly diffusive case, levels farther than the Thouless energy (inverse diffusion time across the dot) from the Fermi level are broadened by the interaction beyond the average level spacing and merge to form a continuous spectrum. The number of discrete levels is hence of the order of 5-20 in typical experiments though such dots may contain thousands of electrons. For less disordered and ballistics dots, the number of discrete levels is of the order of the square root of the number of electrons in the dot.