On the validity region of Fermi-liquid description of 3D strongly correlated systems

The decay of quasiparticles in systems with strongly correlated electrons (SSCE) is investigated. The difference with normal Fermi-liquid (FL) behavior is caused by kinematic interactions. The latter originate (in SSCE) from hopping and mixing interaction which in normal FL just modify bands, but do not cause a decay. Using a diagram technique we derive the lowest-order contribution giving decay and show how it varies with filling and with the position of the Fermi level with respect to the upper Hubbard's sub-band. Examples are given for a simple-cubic 3D-lattice. Due to spin dependence of the vertex functions a big effect on the lifetime of the quasi-particles due to magnetic fields is expected. A possible experimental realization is discussed.