Matter fields near quantum critical point in (2+1)-dimensional U(1) gauge theory

We study chiral phase transition and confinement of matter fields in (2 + 1)-dimensional U(1) gauge theory of massless Dirac fermions and scalar bosons. The vanishing scalar boson mass, r = 0, defines a quantum critical point between the Higgs phase and the Coulomb phase. We consider only the critical point r = 0 and the Coulomb phase with r > 0. The Dirac fermion acquires a dynamical mass when its flavor is less than certain critical value N-f(c), which depends quantitatively on the flavor N-b and the scalar boson mass r. When N-f < N-f(c), the matter fields carrying internal gauge charge are all confined if r not equal 0 but are deconfined at the quantum critical point r = 0. The system has distinct low-energy elementary excitations at the critical point r = 0 and in the Coulomb phase with r not equal 0. We calculate the specific heat and susceptibility of the system at r = 0 and r not equal 0, which can help to detect the quantum critical point and to judge whether dynamical fermion mass generation takes place. (C) 2009 Elsevier B.V. All rights reserved.