Electron-phonon coupling in (kappa)-(BEDT-TTF)(sub 2)Cu(NCS)(sub 2) organic superconductor studied by Raman scattering spectroscopy.

摘要

Low frequency Raman data for (kappa)-(ET)(sub 2)Cu(NCS)(sub 2)(T(sub c) = 10.4 K) are reported. Measurements have been performed in a wide range of temperatures (1.5-100 K) and frequency hardening related to the superconducting transition has been observed for all the low-lying coupled phonons. The measured relative frequency shifts are lower than those previously reported for (kappa)-(ET)(sub 2)Cu(N(CN)(sub 2))Br (T(sub c) = 11.67 K), but the behavior of the two systems is similar and indicates a significant strength of the intermolecular electron-photon coupling. The effects of isotopic substitutions ((sup 13)C(sub 4) (sup 34)S(sub 8) and (sup 2)H(sub 8)) in ET molecules on the low frequency Raman active phonons of (kappa)-(ET(sub 2)Cu(NCS)(sub 2)) are also reported. They give the first direct experimental confirmation to the suggested lattice softening induced by deuteration.