We present the in-plane and c-axis penetration depths of the underdoped cuprates. The pseudogap phase is addressed within the framework of the ordered d-density wave (DDW). The above scenario is considered using a mean-field calculation of the tight binding model which incorporates two types of...

We present a comprehensive optical study of the narrow gap FeSb<Subscript>2</Subscript> semiconductor. From the optical reflectivity, measured from the far infrared up to the ultraviolet spectral range, we extract the complete absorption spectrum, represented by the real part σ<Subscript>1</Subscript>(ω) of the complex optical...</subscript></subscript>

We propose FeSb<Subscript>2</Subscript> to be a nearly ferromagnetic small gap semiconductor, hence a direct analog of FeSi. We find that despite different compositions and crystal structures, in the local density approximation with on-site Coulomb repulsion correction (LDA+U) method magnetic and semiconducting...</subscript>

We investigate polaron formation in a many-electron system in the presence of a local repulsion sufficiently strong to prevent local-bipolaron formation. Specifically, we consider a Hubbard-Holstein model of interacting electrons coupled to dispersionless phonons of frequency ω <Subscript>0</Subscript>. Numerically...</subscript>