Entanglement entropy in the hopping and SSH model.

Entanglement entropy is the core argument of this thesis. After a brief introduction of its properties and a review of the leading theoretical methods for its computation, it is studied in free fermion models, namely the hopping and the SSH model in one dimension. During this preliminary part a code has been created to test numerically the main results. Reached a satisfactory level of reliability for this latter, simulations are used to probe second order symmetry resolved Rènyi entropies (SRRE) in the SSH model. This investigation is carried out considering both finite and infinite subsystems. In the second scenario, recurrent patterns regarding the distribution of SRRE in different charge sectors are obtained and discussed. Supported by numerical data, exact formulae have been achieved to describe the outcomes. In the end, methods are rephrased to extend the analysis to more generic free fermion models.