1. Hard X-ray photoemission study of the Fabre salts (TMTTF)X (X = SbF and PF).
- Author
-
Medjanik, Katerina, de Souza, Mariano, Kutnyakhov, Dmytro, Gloskovskii, Andrei, Müller, Jens, Lang, Michael, Pouget, Jean-Paul, Foury-Leylekian, Pascale, Moradpour, Alec, Elmers, Hans-Joachim, and Schönhense, Gerd
- Subjects
PHOTOEMISSION ,CHARGE transfer ,TEMPERATURE effect ,PHASE transitions ,SOLID state chemistry ,FLUORINE compounds - Abstract
Core-level photoemission spectra of the Fabre salts with X = SbF and PF were taken using hard X-rays from PETRA III, Hamburg. In these salts TMTTF layers show a significant stack dimerization with a charge transfer of 1 e per dimer to the anion SbF or PF. At room temperature and slightly below the core-level spectra exhibit single lines, characteristic for a well-screened metallic state. At reduced temperatures progressive charge localization sets in, followed by a 2nd order phase transition into a charge-ordered ground state. In both salts groups of new core-level signals occur, shifted towards lower kinetic energies. This is indicative of a reduced transverse-conductivity across the anion layers, visible as layer-dependent charge depletion for both samples. The surface potential was traced via shifts of core-level signals of an adsorbate. A well-defined potential could be established by a conducting cap layer of 5 nm aluminum which appears 'transparent' due to the large probing depth of HAXPES (8-10 nm). At the transition into the charge-ordered phase the fluorine 1 s line of (TMTTF)SbF shifts by 2.8 eV to higher binding energy. This is a spectroscopic fingerprint of the loss of inversion symmetry accompanied by a cooperative shift of the SbF anions towards the more positively charged TMTTF donors. This shift does not occur for the X = PF compound, most likely due to smaller charge disproportion or due to the presence of charge disorder. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF