arXiv subjects

Frithjof B. Anders

Publications and source records attributed to Frithjof B. Anders.

77 records · Page 5Linked to original sources

arXiv2002

Composite spin and orbital triplet superconductivity

We show that the two-channel Anderson lattice model leads to the development of an unconventional superconductivity out of a metallic non Fermi-liquid phase. It is characterized by a composite order parameter comprising of a local spin or orbital degree of freedom bound to triplet Cooper pairs with an isotropic and a nearest neighbour form factor. The superconducting transition temperature is band filling dependent and peaks for half filling in the extrem intermediate valence regime and vanishes at integral valence. The gap function is non analytic and odd in frequency, and a pseudo-gap develops in the conduction electron density of states which vanishes as |omega| close to omega=0.

cond-mat.str-el↗

arXiv2001

Composite spin and orbital triplet superconductivity formed out of a Non-Fermi Liquid phase

An unconventional superconducting phase is explored developing out of a non Fermi-liquid phase of the two-channel Anderson lattice model. It is characterized by a composite order parameter comprising of a local spin or orbital degree of freedom bound to triplet Cooper pairs with an isotropic and a nearest neighbour form factor. The superconducting transition temperature peaks in the moderate intermediate valence regime and vanishes at integral valence. The gap function is non analytic and odd in frequency, and a pseudo-gap develops in the conduction electron density of states which vanishes as $|ω|$ close to $ω=0$.

cond-mat.str-el↗

arXiv1999

From ferromagnetism to spin-density wave: Magnetism in the two channel periodic Anderson model

The magnetic properties of the two-channel periodic Anderson model for uranium ions, comprised of a quadrupolar and a magnetic doublet are investigated through the crossover from the mixed-valent to the stable moment regime using dynamical mean field theory. In the mixed-valent regime ferromagnetism is found for low carrier concentration on a hyper-cubic lattice. The Kondo regime is governed by band magnetism with small effective moments and an ordering vector $\q$ close to the perfect nesting vector. In the stable moment regime nearest neighbour anti-ferromagnetism dominates for less than half band filling and a spin density wave transition for larger than half filling. $T_m$ is governed by the renormalized RKKY energy scale $μ_{eff}^2 ^2 J^2ρ_0(μ)$.

cond-mat.str-el↗

arXiv1998

Mixed-valent regime of the two-channel Anderson impurity as a model for UBe_13

We investigate the mixed-valent regime of a two-configuration Anderson impurity model for uranium ions, with separate quadrupolar and magnetic doublets. With a new Monte Carlo approach and the non-crossing approximation we find: (i) A non-Fermi-liquid fixed point with two-channel Kondo model critical behavior; (ii) Distinct energy scales for screening the low-lying and excited doublets; (iii) A semi-quantitative explanation of magnetic-susceptibility data for U$_{1-x}$Th$_x$Be$_{13}$ assuming 60-70% quadrupolar doublet ground-state weight, supporting the quadrupolar-Kondo interpretation.

cond-mat.str-el↗

arXiv1996

Magneto-Resistance in the Two-Channel Anderson Lattice

The paramagnetic phase of the two channel Anderson Lattice model in the Kondo limit is investigated in infinite spatial dimensions using the non-crossing approximation. The resistivity exhibits a Kondo upturn with decreasing $T$, followed by a slow decrease to a finite value at $T=0$. The decrease reflects lattice coherence effects in concert with particle-hole symmetry breaking. The magneto-resistance obeys an approximate scaling relation, decreasing towards coherent Fermi liquid behavior with increasing field. The magnetic field induces a Drude peak in the optical conductivity.

cond-mat↗