Resonant Raman scattering from superconducting single crystals of (BEDT-TTF)2I3

Abstract

Abstract.A study of low energetic resonant Raman scattering of (BEDT-TTF)2I 3 superconducors was performed. The vanishing of phonon bands accompanied by a decrease of the electronic background was observed below T~. We propose a theoretical explanation for this novel effect in terms of the Balseiro-Falicov model of phonon-superconducting amplitude mode interaction.

Resonance Raman Investigations of Low Energetic Modes in the Organic Superconductors αt-(BEDT-TTF)2I3and β-(BEDT-TTF)2IAuI

“…In contrast to [3,4], in the measurements described here, the angle between the crystal surface and the scattered radiation was only about 20°, while in Refs. [3] and [4] this angle was 45°. The measurements at 1.5 K were performed in a liquid helium bath cryostat, all others in a continuous flow-cryostat.…”

“…Recently, in Raman spectra of α t-and ,h-(BEDT-TTF)2I3 by cooling down the crystals from the normal metallic state into the superconducting state, a weakening and shift of low frequency optical phonons around 30 cm -1 as well as a strong decrease in the background was observed [3,4]. As an explanation, in Refs.…”

“…As an explanation, in Refs. [3] and [4], a phonon-superconducting amplitude mode interaction in terms of the Balseiro-Falicov model [5] was proposed. In order to clarify several open questions, more extended measurements were made on ce t-(BEDT-TTF)2I3 as well as on another organic superconductor, β-(BEDT-TTF)2IAuI.…”

Lattice dynamics and electron-phonon coupling in theβ−(BEDT−TTF)2I3Girlando1, Masino2, Visentini3 et al. 2000Phys. Rev. B351380View full textAdd to dashboardCite

“…In the RMA classification, below 220 cm −1 we expect Raman activity for 8 lattice modes, 9 BEDT-TTF intra-molecular modes and one stretching of I − 3 ; in IR we expect 6 lattice modes, 9 BEDT-TTF intra-molecular modes and three I − 3 modes. The modes calculated at the minimum G structure at 120 K are compared with experimental ones, 6,32,43 in Tables III and IV for A u and A g modes, respectively. We have chosen the 120 K temperature since in this way we can compare the normal state phonon frequencies and eigenvectors for the minimum G and the experimental 27 structure.…”

Field and frequency dependent transport in the two-dimensional organic conductor α-(BEDT-TTF)2I3

“…we would not expect to observe a mode of the same intensity in both directions. Recent low temperature Raman experiments [40,41] report a strong mode at 30 cm-l and a weaker one at 38.5 em-I. The authors assign both features to librations of the BEOT-TTF molecule.…”