Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 35: Focused Session: Charge and Spin Transport through Junctions at the Nanometre Scale

TT 35.3: Topical Talk

Donnerstag, 29. März 2012, 10:50–11:30, H 0104

Metallic atomic-size contacts: The role of absorbed noble gas atoms and anisotropic magnetoresistance — •Juan Carlos Cuevas — Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain

In this talk I will review our efforts to resolve two basic puzzles in the context of metallic atomic-size contacts. First, I will discuss how the presence of noble gas atoms affects the electronic transport through atomic contacts. In particular, I will present ab initio results for the conductance of atomic junctions comprising single noble gas atoms (He, Ne, Ar, Kr, and Xe) coupled to gold electrodes. These results show that for the lightest elements (He and Ne) no significant current flows through the noble gas atoms and their effect is to reduce the conductance of the junctions by screening the interaction between the gold electrodes. This explains the observations reported in atomic contacts with adsorbed He atoms. Conversely, the heaviest atoms (Kr and Xe) increase the conductance because of the additional current path provided by their valence p states.

On the other hand, I will address the origin of the anomalous anisotropic magnetoresistance (AMR) observed in different experiments in ferromagnetic atomic-size contacts, which is still under debate. I will present theoretical results that strongly suggest that the anomalous AMR stems from the reduced symmetry of the atomic contact geometries. This reduced symmetry leads to both a great enhancement of the AMR magnitude and an anomalous angular dependence, as compared to bulk devices.