Spring Meeting 2015 in Berlin

2001-2002-2003-2004-2005-2006-2007-2008-2009-2010 - 2011 - 2012 - 2013 - 2014 - 2015 - 2016

Deutsche Physikalische Gesellschaft e. V. (DPG), 31.3.-4.4.2015


Di, 10:45 TT 31.5

Phase transitions and phase separation in undoped and Rh doped CaFe2As2 

— Vladimir Gnezdilov, •Peter Lemmens, Yurii Pachkevich, Tetiana Shevtsova, Masataka Danura, Masakazu Kobayashi, Tasuku Mizukami, Kazutaka Kudo, and Minoru Nohara

Iron-pnictides Ca(Fe1-xRhx)2As2 (x = 0, 0.035 and 0.19) were studied across the tetragonal-orthorhombic and tetragonal collapsed tetragonal phase transitions using Raman spectroscopy. Effects of phase separation were observed in the high-temperature phase for the first time. An orbital order scenario at low temperatures for the Rh doped samples which requires a symmetry lowering down to P4/mnc or I422 without atomic displacements relative to the parent I4/mmm symmetry is discussed. Work supported by RTG-DFG 1953/1, Metrology for Complex Nanosystems.


Di, 11:30 TT 30.8

Raman scattering on the Honeycomb Lattice Iridates A2IrO3 (A=Na,Li) 

— Vladimir Gnezdilov, Robert Bohle, •Peter Lemmens, Soham Manni, Friedrich Freund, and Philipp Gegenwart

Inelastic light scattering studies on single crystals of (Na1−xLix)2(Ir1−yTiy)O3 (x = 0, 0.1, 0.2; y = 0, 0.025) show a polarization and temperature dependent broad band as well as phonon anomalies. We discuss these observations with respect to the relevance of the Kitaev-Heisenberg model and Majorana Fermions for A2IrO3. Work supported by RTG-DFG 1953/1, Metrology for Complex Nanosystems.


Mi, 19:00 TT 70.5 BaMn9[VO4]6(OH)2, a novel candidate for the observation of a Skyrmion lattice 

— •Angela Möller, Kewen Sun, Vladimir Gnezdilov, and Peter Lemmens

The search for topologically stable vortex-like objects (Skyrmions) in insulating chiral magnets lead to their discovery in Cu2OSeO3 [1]. We will show that the combination of certain structural features, such as chirality and frustration might expedite the finding of new candidates of this rare class. A chiral paddle-wheel type of structure featuring geometric frustration has been reported for the metrically cubic title compound with ferrimagnetic, Tc=18 K, and dielectric anomalies [2]. Interestingly, Raman scattering shows magnetoelastic coupling of several phonons but no spontaneous symmetry reduction. This is considered a prerequisite for the existence of a Skyrmion lattice. This work was supported by the NSF (DMR-1149899) and RTG-DFG 1953/1.


Do, 17:30 TT 101.10

Resonant scattering in the topological Dirac semimetal Cd3As2 

— Vladimir Gnezdilov, Azat Sharafeev, •Peter Lemmens, Raman Sankar, and Fangcheng Chou

In the symmetry-broken topological Dirac semimetal with strong spin-orbit coupling, Cd3As2, a pronounced temperature evolution of quasielastic electronic Raman scattering and resonant effects are observed. These effects are then compared to observations in topological insulators, as Bi2Se3. Work supported by RTG-DFG 1953/1, Metrology for Complex Nanosystems and the Laboratory for Emerging Nanometrology Braunschweig, TU Braunschweig.


Do, 18:00 CPP 68.10

ZnO coated TiO2 photoanodes with improved electron transfer for dye sensitized solar cells — •Bo Liu, Peter Lemmens, Andrey Bakin, Andreas Waag, Aidin Lak, Meinhard Schilling, Winfried Daum, and Samir Kumar Pal

ZnO coated TiO2 photoanodes for cost efficient dye sensitized solar cells are prepared using anodization of a metal electrode leading to an array of TiO2 nanotubes. Atomic layer deposition is used for the conformal covering by ZnO. Following hematoporphyrin sensitization the improved electron transfer is probed using time resolved fluorescence. Work supported by RTG-DFG 1953/1, Metrology for Complex Nanosystems and the Laboratory for Emerging Nanometrology, TU Braunschweig.