________________________________________ * Author for correspondence; E-mail: Int. J. Chem. Sci.: 10(2), 2012, 1157-1166 ISSN 0972-768X www.sadgurupublications.com AN EVALUATION OF OPTICAL PARAMETERS OF HIGH- TEMPERATURE SUPERCONDUCTORS SANJU KUMARI a , SOBHA RANI b , S. KUMAR c and LALIT K. MISHRA * Department of Physics, Magadh University, BODH GAYA – 824234 (Bihar) INDIA a Department of Physics, K. S. T. College, Shalmpur, SOHSARAI – 803118, Biharsarif, Nalanda (Bihar) INDIA b Department of Physics, G. D. Mahila College Harinaut, Biharsarif , NALANDA (Bihar) INDIA c Departnent of Physics, Nalanda College, Biharsarif, NALANDA (Bihar) INDIA ABSTRACT Frequency dependent scattering rate and effective mass of electron were evaluated for two high Tc-superconductors using extended Drude model at different temperatures. Our theoretically evaluated result for scattering rate is large and effective mass is small in comparison with experimental data for the given temperatures. However, the trend for both the scattering rate and effective mass are in agreement with the experimental data and also with other theoretical workers. Key words: Frequency dependent scattering rate, Effective mass, High Tc-superconductor, Optical parameters, Dirty limit, K-K relation. INTRODUCTION The optical reflectivity measurement is a powerful probe for the study of the electronic structure of solids. It can provide much information on the conduction bands as well as valence bands of the crystals through inter band transition. It is a interesting problem for Bi-based cuprates. How the excitations within Bi 2 -O 2 layer affect those within Cu-O 2 layer and how the Optical transitions differ from those of Y-Ba-Cu-O and La-Sr-Cu-O. The optical reflectivity spectra of single crystal Bi-based cuprates Bi 2 Sr 2 CaCu 2 O 8+x and Bi 2 Sr 2 CuO 6+X were measured 1 in a wide energy range from 0.5 to 40 eV and analyzed through the Kramers-Kronig (KK) relation. The obtained spectra are different from other superconducting cuprates such as (LaSr) 2 CuO 4 and YBa 2 CuO 4 because of existence of characteristic BiO 2 layer. The optical excitation starts from 2 eV or higher energy so it is