A time-dependent tunneling approach to RIXS and other core-hole spectroscopies

We introduce a numerical approach to calculate the Resonant Inelastic X-Ray Scattering (RIXS) in strongly correlated systems. Since accounting for intermediate processes involved in RIXS requires the knowledge of all eigenstates of the Hamiltonian, these computations have remained very challenging. We recast the calculation as a tunneling problem that can be readily solved by means of the time-dependent DMRG method and does not require a full knowledge of the excitations. This powerful formulation overcomes all the hurdles imposed by other techniques that rely on explicitly obtaining dynamical spectral functions. Results for the Hubbard model are achieved with minimal effort on large systems using a fraction of the states --and simulation time-- required by the dynamical DMRG formulation. These ideas can be readily applied without modification away from equilibrium.