Physics – Condensed Matter – Quantum Gases
Scientific paper
2012-02-23
Physics
Condensed Matter
Quantum Gases
15 pages, 11 figures
Scientific paper
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.
Hofmann Felix
Potthoff Michael
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