Isotope effect in superconductivity on 13C substituted βH-(BEDT-TTF)2I3
Résumé
We have investigated the resistive superconducting transition of βH-(ET)2I3 crystals in which the two inner carbon atoms, in the center of the ET molecule, have been substituted with 13C isotopes. We stabilised the βH state of (ET)2I3 at low temperature via the appropriate cooling procedure in a He gas pressure apparatus ("Orsay process"). The superconducting transition of 13C substituted samples was found to be Tc = 7.80±0.05 K (at midpoint), namely 0.20K lower than that of standard 12C samples (Tc = 8.0±0.1 K). We have taken care that both types of samples were measured in the same conditions and that p(T) data were free from cracks which can broaden the superconducting transition. This large and regular isotope shift of Tc is in contrast with most of the previous results in organic superconductors and suggests the existence of a superconductivity mechanism mediated by the coupling of electrons with the intramolecular phonom models.
Mots clés
- Unsaturated compounds
- Carbon
- Cooling
- Crystals
- Electrons
- Iodine compounds
- Isotopes
- Phonons
- Salts
- Orsay process
- Organic superconductors
- Isotope effect
- Electron phonon coupling
- Bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) salts
- Superconductivity
- Superconducting transition temperature
- Superconducting materials
- Stabilization