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Detailed Analysis of Quantum Phase Transitions Within the u (2) Algebra

2010; Institute of Physics; Volume: 54; Issue: 4 Linguagem: Inglês

10.1088/0253-6102/54/4/01

1572-9494

L. Fortunato, Leo Sartori,

Spectroscopy and Quantum Chemical Studies

We analyze in detail the quantum phase transitions that arise in models based on the $u(2)$ algebraic description for bosonic systems with two types of scalar bosons. First we discuss the quantum phase transition that occurs in hamiltonians that admix the two dynamical symmetry chains $u(2)\supset u(1)$ and $u(2)\supset so(2)$ by diagonalizing the problem exactly in the $u(1)$ basis. Then we apply the coherent state formalism to determine the energy functional. Finally we show that a quantum phase transition of a different nature, but displaying similar characteristics, may arise also within a single chain just by including higher order terms in the hamiltonian.