Well-defined quasiparticles in interacting metallic grains

TL;DR

This paper demonstrates the existence of well-defined quasiparticles in interacting metallic grains by analyzing spectral functions, and introduces a high-accuracy computational method for zero-temperature spectral properties.

Contribution

It shows that spectral functions are dominated by a single state, indicating infinite-lifetime quasiparticles, and applies DMRG to compute spectral functions in mesoscopic systems.

Findings

Spectral functions are dominated by a single state.

Quasiparticles have infinite lifetime in these systems.

High-accuracy DMRG calculations of spectral functions are possible.

Abstract

We analyze spectral functions of mesoscopic systems with large dimensionless conductance, which can be described by a universal Hamiltonian. We show that an important class of spectral functions are dominated by one single state only, which implies the existence of well-defined (i.e. infinite-lifetime) quasiparticles. Furthermore, the dominance of a single state enables us to calculate zero-temperature spectral functions with high accuracy using the density-matrix renormalization group. We illustrate the use of this method by calculating the tunneling density of states of metallic grains and the magnetic response of mesoscopic rings.