We are interested in developing theoretical descriptions of the novel electric, magnetic and optical behavior of low dimensional (quasi-one-dimensional and quasi-two-dimensional) materials with strong Coulomb repulsive interaction among the electrons. While our research is primarily driven by fundamental curiosity, in many cases the materials we are investigating, -- often in collaboration with experimentalists, -- hold exciting technological promises. Our research is also highly interdisciplinary, and spans condensed matter physics, materials chemistry and optics.

    Mean field and perturbative techniques often fail for low dimensional systems with strong Coulomb interactions, which therefore lie outside the domain of textbook solid state physics. The most well known members of this class of materials are of course the cuprate high temperature superconductors, the mechanism of superconductivity in which remains unresolved two decades after they were discovered. It is important to realize, however, that there occur many other systems, -- semiconducting, conducting and superconducting, -- that exhibit exotic behavior associated with strong Coulomb interactions and narrow one-electron bandwidths. We have been mostly (but not entirely) interested in low dimensional organic materials: conjugated polymeric and molecular semiconductors,  semiconducting single-walled carbon nanotubes and conducting and superconducting organic charge-transfer solids. We are also interested in several different classes of semiconducting inorganic oxides.

    Broadly speaking, there are two classes of behavior we investigate. The first class involves photonics, - the interaction of light with matter. Here we are interested in high energy excited states that are accessible in linear and nonlinear optical absorption measurements (1, 2). Our interest here includes also optoelectronics and spintronics. We have extensive on-going collaborations with experimentalists in this line of research.

    The second class of behavior we are interested in involves broken symmetry. Here we are interested in understanding the peculiar metal-to-insulator, magnetic insulator-to-insulator and insulator-to-superconductor transitions that are observed in many low-dimensional systems, in particular, the organic charge-transfer solids. We strongly believe that the mechanisms of exotic superconductivity in the cuprates and the organics (as well as possibly other exotic superconductors) are related.