Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 13: Electronic Structure of Surfaces II

O 13.11: Talk

Monday, March 16, 2015, 17:45–18:00, MA 041

Unconventional surface reconstruction of Na₂IrO₃ with persistent energy gap — •Felix Lüpke^1,2, Soham Manni^3,4, Steven C. Erwin⁵, Igor I. Mazin⁵, Philipp Gegenwart⁴, and Martin Wenderoth¹ — ¹IV. Physikalisches Institut, Georg-August-Universität Göttingen, D-37077 Göttingen, Germany — ²Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany, and JARA-Fundamentals of Future Information Technology — ³I. Physikalisches Institut, Georg-August-Universität Göttingen, D-37077 Göttingen, Germany — ⁴Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, D-86159 Augsburg, Germany — ⁵Center for Computational Materials Science, Naval Research Laboratory, Washington, DC 20375, USA

Na₂IrO₃ is an intriguing material for which theoretical predictions, so far unverified, have been made that the surface of Na₂IrO₃ should exhibit a clear signature of the quantum spin Hall effect. We studied the surface of Na₂IrO₃ using scanning tunneling microscopy, spectroscopy and density-functional theory calculations. We observed two types of surface terminations with different surface periodicity and Na content. By comparing bias-dependent experimental topographic images to simulated images, we determined the detailed atomistic structure of both observed surfaces. The found dramatic structural changes are highly unusual and cast doubt on any prediction of surface properties based on bulk electronic structure. Indeed, we found no indication of the predicted quantum spin Hall behavior.