Starts 28 Feb 2013 11:30
Ends 28 Feb 2013 20:00
Central European Time
Leonardo da Vinci Building Luigi Stasi Seminar Room
Strada Costiera, 11 I - 34151 Trieste (Italy)
We develop the theoretical study of a novel physical system, in the context of ultracold gases. We investigate the physical behavior of a resonant Bose-Fermi mixture, namely, an ultracold gas made of both bosons and fermions, with a strong attractive interaction between these two components. We study homogeneous density and mass imbalanced mixtures from weak- to strong- coupling limit, comparing the results obtained with two different theoretical approaches, a many-body diagrammatic approach (the T- matrix approximation) and Quantum Monte Carlo method. By using many-body diagrammatic methods we first obtain the finite-temperature phase diagram and the thermodynamic properties of the system. We observe the presence of a quantum phase transition from the condensed (superfluid) to the normal (molecular) phase. Developing the zero-temperature limit of the same Green’s function formalism we study the effect of density and mass imbalances for the Bose-Fermi mixture. By using the corresponding retarded propagators we calculate the spectral weight functions and the dispersions of bosons and fermions. We apply for the first time the Quantum Monte Carlo method with Fixed-Node approximation to investigate resonant Bose-Fermi mixture, from weak to strong boson-fermion attraction. Two different nodal surfaces are used as trial wave functions in the two regimes. We obtain the equation of state of a density imbalanced mixture and we observe the presence of the quantum phase transition through the crossing of the energies, calculated with their respective trial wave functions. A phase diagram in the coupling and boson-fermion concentration variables is derived and the occurrence of phase separation is discussed. We compare Quantum Monte Carlo results to T-matrix calculations, finding an interesting agreement between the results.
  • M. Poropat