Thermalization of Interacting Fermions and Delocalization in Fock space

Understand

By means of exact diagonalization, we investigate the onset of 'eigenstate thermalization' and the crossover to ergodicity in a system of 1D fermions with increasing interaction.

• We show that the fluctuations in the expectation values of the momentum distribution from eigenstate to eigenstate decrease with increasing coupling strength and system size.
• It turns out that these fluctuations are proportional to the inverse participation ratio of eigenstates represented in the Fock basis.
• We demonstrate that eigenstate thermalization should set in even for vanishingly small perturbations in the thermodynamic limit.