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Heavy Quasiparticles in Yb Compounds: The Renormalized Band Approach

100%

Zwicknagl G.

Acta Physica Polonica A

2014

vol. 126

issue 1

286-287

Results for the magnetic-field-induced changes of the heavy quasiparticles in YbRh_{2}Si_{2} are presented. The bands are determined by means of the Renormalized Band method. The progressive de-renormalization of the quasiparticles in the magnetic field, as well as the many-body enhancement of the Zeeman splitting are accounted for, using field-dependent quasiparticle parameters deduced from Numerical Renormalization Group studies.

Partial Localization of Correlated Electrons in an Orbitally Degenerate Narrow Band: Spin Dependent Masses, Saturated Ferromagnetism, and the Effective s-d Model

51%

Jędrak J., Spałek J., Zwicknagl G.

We determined the localization threshold in a partially filled and doubly degenerate model of correlated electrons. Particular emphasis is put on a non-integer band filling n≥1, when the system decomposes into the localized and the itinerant subsystems; this situation is described by an effective s-d model. A simultaneous transition to the ferromagnetic state is discussed as driven by the Hund rule coupling combined with the effective field coming from the correlations. The dependence of the quasiparticle mass on the spin direction appears naturally in the spin-polarized phase and is attributed to the electron correlation effects, as is also a metamagnetic transition in an applied field. Although the main results were obtained within the saddle point slave-boson approach, their qualitative features are discussed in general terms, i.e. as a transition from quantum-mechanical indistinguishability of particles forming the Fermi fluid to a two-component situation.

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2 Acta Physica Polonica A

1 2014

1 2007

2 Zwicknagl G.

1 Jędrak J.

1 Spałek J.

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Heavy Quasiparticles in Yb Compounds: The Renormalized Band Approach

Partial Localization of Correlated Electrons in an Orbitally Degenerate Narrow Band: Spin Dependent Masses, Saturated Ferromagnetism, and the Effective s-d Model