BEDT-TTF organic superconductors: the entangled role of phonons

Abstract

We calculate the lattice phonons and the electron-phonon coupling of the organic superconductor κ-(BEDT-TTF)_2 I_3, reproducing all available experimental data connected to phonon dynamics. Low-frequency intra-molecular vibrations are strongly mixed to lattice phonons. Both acoustic and optical phonons are appreciably coupled to electrons through the modulation of the hopping integrals (e-LP coupling). By comparing the results relevant to superconducting κ- and β-(BEDT-TTF)_2 I_3, we show that electron-phonon coupling is fundamental to the pairing mechanism. Both e-LP and electron-molecular vibration (e-MV) coupling are essential to reproduce the critical temperatures. The e-LP coupling is stronger, but e-MV is instrumental to increase the average phonon frequency.

arXiv comment4 pages, including 4 figures. Published version, with Ref. 17 corrected after publication

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• Pairing Symmetry Competition in Organic Superconductors
• Investigating polaron transitions with polar molecules
• Real space imaging of the metal - insulator phase separation in the band width controlled organic Mott system $\kappa$-(BEDT-TTF)${}_2$Cu[N(CN)${}_2$]Br
• Bandwidth tuning triggers interplay of charge order and superconductivity in two-dimensional organic materials
• Towards the parameterisation of the Hubbard model for salts of BEDT-TTF: A density functional study of isolated molecules
• Coulomb Enhanced Superconducting Pair Correlations in the Frustrated Quarter-Filled Band
• On the Relationship Between the Critical Temperature and the London Penetration Depth in Layered Organic Superconductors