Novel approach to nonlinear susceptibility

Original · EN

The calculation of the third order susceptibility still is a long standing fundamental problem of particular importance in nonlinear nanooptics: Indeed, cancellation of size-dependent terms coming from uncorrelated excitations is expected, but up to now shown for very simple Hamiltonians only. Using a many-body theory recently developed to handle interacting close-to-bosons, we prove it here for arbitrary H. This new formalism actually provides the first clean way to calculate nonlinear susceptibilities, with results different from previous ones.