Dresden 2014 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 101: Transport - Poster Session

TT 101.7: Poster

Thursday, April 3, 2014, 15:00–19:00, P2

Conductance Quantization in Rare-Earth-Metal Nanocontacts — •Oliver Berg¹, Christoph Sürgers¹, and Hilbert v. Löhneysen^1,2 — ¹Physikalisches Institut, Karlsruher Institut für Technologie, 76049 Karlsruhe — ²Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe

We present conductance measurements of Gd, Dy, and Ce obtained on mechanically controlled break-junctions (MBCJ) made from polycrystalline wires at l-He temperatures. The contact formation and switching between metallic and tunneling conductance G is investigated in dependence of the electrode distance Δ x. From a number of measurements of G(Δ x), exhibiting conductance plateaus, we obtain conductance histograms. We focus on the conductance G^* of the last plateau before with increasing Δ x, G enters the tunneling regime. While for Gd and Dy the last "plateau" occurs at G^*≈ 0.6 G₀ and 0.9 G₀ (G₀=2e²/h), respectively, G^*≃ 1.7 G₀ is observed for Ce. For Gd and Dy the 4f state is far below the Fermi level and does not contribute to the electronic transport. A possible explanation for the large G^* value of Ce is the additional contribution from the 4f state being shifted toward the Fermi level, when cooling the sample through the γ−α phase transition.