Dresden 2014 – scientific programme

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MA: Fachverband Magnetismus

MA 55: Poster II

MA 55.109: Poster

Friday, April 4, 2014, 10:30–13:30, P2

Pyrochlore Iridates: Possible Candidates for the Realization of Weyl Nodes — •Andreas Wörfel¹, Matthias Opel¹, Stephan Geprägs¹, and Rudolf Gross^1,2 — ¹Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany — ²Physik-Department, Technische Universität München, 85748 Garching, Germany

Pyrochlore iridates A₂Ir₂O₇ (A=Y or a rare-earth ion) offer a promising system for studying the interplay of strong spin-orbit coupling, electronic correlations, and band topology effects. Novel phases such as axial or topological insulators, and Weyl semimetals have been predicted in these compounds [1]. In particular, Nd₂Ir₂O₇ is proposed to exhibit Weyl semimetal nodes, where two non-degenerate bands touch each other creating a local linear dispersion. These nodes are topologically protected making Weyl states absolutely robust to perturbations.

Here, we report on a detailed study of the structural, magnetic, and magnetotransport properties of bulk samples as well as thin films of Nd₂Ir₂O₇. Epitaxial Nd₂Ir₂O₇ thin films were deposited on single-crystalline Y:ZrO₂ (111) substrates using laser-MBE, whereas polycrystalline bulk Nd₂Ir₂O₇ samples were fabricated by a standard solid state reaction. These samples show a metal to insulator transition (MIT) at around T_MIT≃33 K. The MIT is accompanied by a bifurcation of the magnetic susceptibility in field-cooled (FC) and zero-field-cooled (ZFC) conditions, suggesting the existence of a magnetic long-range ordered state for temperatures T<T_MIT.

[1] X. Wan et al., Phys. Rev. B 83, 205101 (2011).