00 1 Exact solutions for the periodic Anderson model in 2 D : A Non - Fermi liquid state in normal phase

Presenting exact solutions for the two dimensional periodic Anderson model with finite and nonzero on-site interaction U > 0, we are describing a rigorous non-Fermi liquid phase in normal phase and 2D. This new state emerges in multi-band interacting Fermi systems above half filling, being generated by a flat band effect. The momentum distribution function n~k together with its derivatives of any order is continuous. The state possesses a well defined Fermi energy (eF ), but the Fermi momentum concept is not definable, so the Fermi surface in ~k-space is missing. The state emerges in the vicinity of a Mott insulating phase when lattice distortions are present, is highly degenerated and paramagnetic. A gap is present at high U in the density of low lying excitations. During low lying excitations, quasi-particles are not created above the Fermi level, only the number of particles at eF increases. PACS No. 05.30.Fk, 67.40.Db, 71.10.-w, 71.10.Hf, 71.10.Pm Typeset using REVTEX 1