A FL* approach to High Tc cuprates

The FL* liquid is a concept introduced some years ago to describe an electronic Fermi liquid where the particle excitations are not only the standard spin 1/2 charged electrons, but also particle excitations carrying charge but spinless, named holons, and carrying only spin 1/2 but neutral, named spinons. Such kind of excitations have been introduced immediately after the discovery of high Tc superconductivity in the cuprates by Anderson and Kivelson, mainly relying on analogy with one-dimensional models, but the idea that in planar systems they can coexist with bound states of them in the form of an electronic Fermi liquid is quite recent. It has benn shown that to the FL* liquid one can apply two suitable topological versions of the Luttinger theorem on the Fermi volume. In this thesis it is analyzed a possible FL* nature of the low-energy physics of high Tc cuprates, with a verification of the Luttinger theorem, to an approach proposed mainly by Sachdev, based upon a suitabky revised versione of the RVB formalism pioneered by Anderson. A brief comment is added on a gauge approach with semionic statistics of holons and spinons, originally proposed by Laughlin, where an initially overlooked FL* nature seems to emerge. Finally a comparison of some experimental data with results obtained in the FL* approach to cuprates is discussed.