Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 53: Correlated Electrons: Heavy Fermions

TT 53.10: Talk

Thursday, March 14, 2013, 12:00–12:15, H19

Non-Fermi liquid picture and superconductivity in heavy fermion systems — •Steffen Sykora¹ and Klaus W. Becker² — ¹IFW Dresden, D- 01171 Dresden, Germany — ²Department of Physics, TU Dresden, D-01069 Dresden, Germany

We study the S=1/2 Kondo lattice model which is widely used to describe heavy fermion behavior. In conventional treatments of the model a hybridization of conduction and localized f electrons is introduced by decoupling the Kondo interaction. However, such an approximation has the detrimental effect that a breaking of a local gauge symmetry is imposed which implicates that the local f occupation n_i^f is no longer conserved. To avoid such an artifact, we treat the model in an alternative approach based on the Projective Renormalization Method (PRM). Thereby, within the conduction electron spectral function we identify the lattice Kondo resonance as an almost flat incoherent excitation near the Fermi surface which is composed of conduction electron creation operators combined with localized spin fluctuations. This leads to a new concept of the Kondo resonance without having to resort to a symmetry breaking and Fermi liquid theory. Based on this new picture we develop a microscopic theory for superconductivity in heavy fermion systems. Thereby we study the momentum-dependence of the superconducting order parameter for singlet as well as triplet pairing. We show that in particular the triplet pairing components are strongly affected by the incoherent excitations found to be responsible for the Kondo resonance.