The infrared properties of Bi_(2.07)Sr_(1.8)CuO_(6+#delta#) and Bi_2Sr_(1.6)La_(0.4)CuO_(6+#delta#) superconductors

摘要

The infrared reflectivity of the bismuth-based high-T_c superconductors Bi_(2.07)Sr_(1.8)CuO_(6+#delta#) (2201) with T_c = 7 K and Bi_2Sr_(1.6)La_(0.4)CuO_(6+#delta#) (La2201) with T_c = 30 K have been measured between 25 and 8000 cm~(-1) at temperatures between 5 and 300 K. The temperature- and frequency-dependent far-infrared part of the spectrum is analyzed. We discuss the influence of La presence on the infrared-active phonons.