Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 53: Low-Dimensional Systems: 1D - Theory

TT 53.10: Vortrag

Mittwoch, 9. März 2016, 17:30–17:45, H23

Properties of the single-site reduced density matrix in the Bose-Bose resonance model in equilibrium and in quantum quenches — •Florian Dorfner and Fabian Heidrich-Meisner — Ludwig-Maximilians-Universität München, Germany

We study properties of the single-site reduced density matrix in the Bose-Bose resonance model as a function of system parameters. This model describes a single-component Bose gas with a resonant coupling to a molecular state, here defined on a lattice. We study the eigenstates of the single-site reduced density matrix in the various quantum phases of this system. Since the Hamiltonian conserves only the global particle number but not the number of bosons and molecules individually, these eigenstates, referred to as optimal modes, can be nontrivial linear combinations of bare eigenstates of the molecular and boson particle number. We numerically analyze the optimal modes and their weights, the latter giving the importance of the corresponding state, in the ground state of the Bose-Bose resonance model and find that the single-site von Neumann entropy is sensitive to the position of the phase boundaries. We explain the structure of the optimal modes and their weight spectra using perturbation theory and via a comparison to results for the one-species Bose-Hubbard model. Further, we study the dynamical evolution of the optimal modes and of the single-site entanglement entropy in two quantum quenches that cross phase boundaries between different phases of the model. For our numerical calculations, we use exact diagonalization and the density matrix renormalization group method.