OPTICAL STUDY OF THE ELECTRONIC-STRUCTURE AND ELECTRON MOLECULAR VIBRATIONAL COUPLING IN A NOVEL ORGANIC SUPERCONDUCTOR KAPPA-(BEDT-TTF)2CU[N(CN)2]CL0.5BR0.5
Oo. Drozdova et al., OPTICAL STUDY OF THE ELECTRONIC-STRUCTURE AND ELECTRON MOLECULAR VIBRATIONAL COUPLING IN A NOVEL ORGANIC SUPERCONDUCTOR KAPPA-(BEDT-TTF)2CU[N(CN)2]CL0.5BR0.5, Synthetic metals, 64(1), 1994, pp. 17-26
Reflectance spectra of a new ambient-pressure superconductor, kappa-(B
EDT-TTF)2Cu[N(CN)2]Cl0.5Br0.5 (T(c) = 11.3 K), where BEDT-TTF is bis(e
thylenedithio)tetrathiafulvalene, are measured in the range from 750 t
o 5500 cm-1 and from 9000 to 40 000 cm-1 for different polarizations.
The detailed analysis of the infrared conductivity, obtained after a K
ramers-Kronig transformation, is performed in the framework of the app
roach, based on the 'phase phonons' theory of M.J. Rice, with the help
of special transformation of the experimental data. Parameters of the
electronic subsystem and electron-molecular vibration coupling are de
termined. The determined 'total' dimensionless coupling constant (lamb
da) is compared with those of the organic super conductors kappa-(BEDT
-TTF)2Cu(NCS)2 (T(c) = 10.4 K) and (BEDT-TTF)4Hg2.89Br8 (T(c) = 4.3 K)
. It is found that a larger lambda produces a larger T(c) in accordanc
e with the known Bardeen-Cooper-Schriffer formula for T(c).