Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 87: Low-Dimensional Systems: Molecular Conductors (jointly with CPP, HL, MA, O)

TT 87.2: Talk

Thursday, March 19, 2015, 09:45–10:00, H 3010

Observation of charge localization and the charge ordering transition in (TMTTF)₂AsF₆ using NEXAFS — •Katerina Medjanik¹, Alisa Chernenkaya², Sergej Nepijko², Gunnar Öhrwall¹, Pascale Foury-Leylekian³, Pere Alemany⁴, Enric Canadell⁵, Gerd Schönhense², and Jean-Paul Pouget³ — ¹Lund University, MAX IV Laboratory, 22100 Lund, Sweden — ²Institut für Physik, JOGU, 55099 Mainz, Germany — ³Laboratoire de Laboratoire de Physique des Solides, Université Paris-Sud, 91405 Orsay, France — ⁴IQTCUB, Universitat de Barcelona, 08028 Barcelona, Spain — ⁵ICMAB-CSIC, 08193 Bellaterra, Spain

High-resolution near-edge X-ray absorption fine structure (NEXAFS) measurements at MAX II, Lund (beamline I1011 [1]) were performed on a (TMTTF)₂AsF₆ [2] single crystal upon cooling from room temperature to 90 K. Systematic shifts of different spectral features of the F 1s and S 2p signal by up to 0.8 eV to opposite sides on the photon-energy scale with respect to the spectra at room temperature have been detected. Most likely, the shift of the S 2p signal is connected with the breakdown of itinerant conductivity and loss of screening when entering the charge-localization regime.The appearance of a new F 1s pre-edge signal upon entry into the charge ordering (CO) phase at 90 K is a clear fingerprint of the reorganization of the anions in the layered material and changing in the dimerization of molecular orbitals with respect to room temperature.Project funded by DFG through SFB Transregio 49.

[1] I. A. Kowalik et al., J. Phys.: Conf. Ser. 211, 012030 (2010);

[2] M. de Souza et al., Physica B, 405, 92 (2010).