title: Shell-filling effect in the entanglement entropies of spinful fermions.
abstract: We consider the von Neumann and Rényi entropies of the one-dimensional quarter-filled Hubbard model. We observe that for periodic boundary conditions the entropies exhibit an unexpected dependence on system size: for L=4 mod 8 the results are in agreement with expectations based on conformal field theory, while for L=0 mod 8 additional contributions arise. We explain this observation in terms of a shell-filling effect and develop a conformal field theory approach to calculate the extra term in the entropies. Similar shell-filling effects in entanglement entropies are expected to be present in higher dimensions and for other multicomponent systems.
authors.affiliation: The Rudolf Peierls Centre for Theoretical Physics, Oxford University, Oxford OX1 3NP, United Kingdom.
authors.forename: Fabian H L
authors.initials: FH
authors.lastname: Essler
authors.affiliation: Institut für Theoretische Physik, Universität Innsbruck, A-6020 Innsbruck, Austria.
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Läuchli
authors.affiliation: Dipartimento di Fisica dell'Università di Pisa and INFN, 56127 Pisa, Italy.
authors.forename: Pasquale
authors.initials: P
authors.lastname: Calabrese