1202.5149 (Felix Hofmann et al.)

Doublon dynamics in the extended Fermi Hubbard model    [PDF]

Felix Hofmann, Michael Potthoff

Two fermions occupying the same site of a lattice model with strongly
repulsive Hubbard-type interaction form a doublon, a long-living excitation the
decay of which is suppressed because of energy conservation. By means of an
exact-diagonalization approach based on the Krylov-space technique, we study
the dynamics of a single doublon, of two doublons, and of a doublon in the
presence of two additional fermions prepared locally in the initial state of
the extended Hubbard model. The time dependence of the expectation value of the
double occupancy at the different sites of a large one-dimensional lattice is
analyzed by perturbative arguments. In this way the spatiotemporal evolution of
the doublon, its decay on a short time scale and the long-time average of the
total double occupancy can be understood. We demonstrate how the dynamics of a
doublon in the initial state is related to the spectrum of two-fermion
excitations obtained from linear-response theory, we work out the difference
between doublons composed of fermions vs. doublons composed of bosons and show
that despite the increase of phase space for inelastic decay processes, the
stability of a doublon is enhanced by the presence of additional fermions on an
intermediate time scale.

View original: http://arxiv.org/abs/1202.5149