Theoretical modeling of some low dimensional quantum spin systems and charge transport in a few organic materials

Abstract

Electronic correlations play the central role in governing many fundamental aspects of materials, which include excitation characteristics, thermodynamic and dynamic behavior of systems, ranging from small molecules to solids and complex systems like DNA and protein. Depending upon the strength of electronic correlations, the materials world can be categorized into two broad classes: (i) strongly correlated and (ii) weakly correlated electronic systems. In strongly correlated systems, the Coulomb interaction energy is comparable or greater than the kinetic energy. Examples of a few strongly correlated electronic systems include cuprates, rare-earth lanthanides and actinides, vanadates, manganites and transition metal oxides. A number of novel properties emerge due to electron-electron interaction [1–5]. Over past few decades, the strongly correlated materials have been of great interest to both theorists and experimentalists alike, owing to their unusual electronic and magnetic properties [6–22]. Because of the advancement of quantum mechanics, the essential features of these wide class of materials are explained by many-particle theory since the independent particle picture fails to describe the strongly correlated systems. However, the weakly correlated materials in which the electron-electron interaction is weak or negligible, can be well described by various one electron theories.