[en] Renormalization methods in various solid state problems (e.g., the Kondo effect) are analyzed from a qualitative vantage point. Our goal is to show how the renormalization procedure works, and to uncover a few simple general ideas (universality, phenomenological descriptions, etc...)

No abstract available

[en] Understanding the emergence and subsequent behavior of heavy electrons in Kondo lattice materials is one of the grand challenges in condensed matter physics. From this perspective we review the progress that has been made during the past decade and suggest some directions for future research. Our focus will be on developing a new microscopic framework that incorporates the basic concepts that emerge from a phenomenological description of the key experimental findings. (report on progress)

[en] The Kondo insulating materials present a particularly simple limiting case of the strongly correlated electron lattice problem: one occupied f-state interacting with a single half-filled conduction band. Experiment shows that the solution to this problem has some remarkably simple aspects. Optical conductivity data display the strong coupling nature of this physics

[en] The interplay between vibrational modes and Kondo physics is a fundamental aspect of transport properties of correlated molecular conductors. We present theoretical results for a single molecule in the Kondo regime connected to left and right metallic leads, creating the usual coupling to a conduction channel with left-right parity even. A center-of-mass vibrational mode introduces an additional phonon-assisted tunneling through the antisymmetric odd channel. A non-Fermi-liquid fixed point, reminiscent of the two-channel Kondo effect, appears at a critical value of the phonon-mediated coupling strength. Our numerical renormalization-group calculations for this system reveal non-Fermi-liquid behavior at low temperatures over lines of critical points. Signatures of this strongly correlated state are prominent in the thermodynamic properties and in the linear conductance.

[en] A brief discussion of the basic physics, some current issues and new results of heavy fermions are presented, emphasizing the importance of the antiferromagnetic correlations between f moments. For a Fermi liquid like fixed point, a nonperturbative approach to incorporate antiferromagnetic correlations into the fixed point is outlined. A possible two-fluid behavior of the heavy fermion micromagnetism and metamagnetism is proposed based on experimental results accumulated in the last several years. A simple model possessing the two-fluid behavior, the underscreened Kondo problem, is studied as an example. Its extension to more realistic situations is discussed. The intermediate coupling fixed point of the overscreened Kondo problem is thoroughly studied using the perturbative renormalization group method. Various thermodynamic and dynamic quantities are calculated and their exponents are determined

[en] Assuming the BCS mechanism, we have adopted the Anderson-model Hamiltonian to investigate if the ferromagnetic and the superconducting states can coexist in the Kondo-type heavy fermion superconductors. The results show that the coexistent state is unstable

No abstract available

[en] We study here the underscreened Kondo-lattice model, where the localized spins S=1 are not completely screened by the s=((1)/(2)) conduction electron spins. It results a coexistence of a 5f magnetic order and a Kondo effect which can qualitatively account for the behavior of some uranium compounds

[en] The theory of Kondo effect in superconductors put forward by Matsuura, Ichinose and Nagaoka is generalized to a two-band system. Analytic expressions for the variation of the critical temperature due to Kondo impurities are obtained. (author)