Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 18: Correlated Electrons: Quantum Impurities, Kondo Physics 2

TT 18.12: Talk

Tuesday, March 27, 2012, 12:30–12:45, H 3005

Indirect magnetic exchange and Kondo screening in one-dimensional metals with few magnetic impurities — •Andrej Schwabe and Michael Potthoff — University Hamburg, Hamburg, Germany

The Kondo effect of one impurity coupled to a metallic substrate by an exchange interaction J is known as an impressive many-body effect which is regarded as well understood. Adding another impurity may cause two separate Kondo effects, but can also introduce a new inter impurity RKKY coupling. The competition between both interactions gives rise to different parameter regimes: In the large J or large distance limit both impurities are separately screened while in the weak J or small distance limit they form a non-local spin which itself can be screened by the substrate.
We apply our variational matrix-product states code (VMPS) which is based on the implementation of the corrected one-site algorithm and exploits U(1) symmetries. Calculations are presented for three impurities coupled to a nano chain within an Anderson model. We discuss its manifold properties by referring to results for the single and two impurity model. We focus explicitly on a substrate of finite size and discuss the consequences of finite-size gaps and symmetry.
The transition from the diluted case with few impurities to the dense lattice with one impurity on every substrate site, leads to further, even richer physics, including the exhaustion problem and magnetic long-range order. General trends considering the transition to dense chains are given.