Seminarium Fizyki Materii Skondensowanej

We consider a coupled boson-fermion model in two dimensions, thatdescribes itinerant fermions hybridizing with localized bosons composed ofpairs of tightly bound opposite-spin fermions. We trace out the fermionicdegrees of freedom and perform a Monte Carlo simulation for the effectiveclassical Hamiltonian of boson phases. We find that the fermions generatean effective long-range temperature-dependent boson-boson coupling that atlow temperature generates a quasi long range order. With increasingtemperature the Kosterlitz-Thouless transition is observed. Theboson-fermion interaction also modifies properties of the fermionsubsystem leading to a disordered bosonic insulator at high temperature inthe strong coupling regime.