高Tc超导体的室温飞秒时间分辨谱研究

Room Temperature Femtosecond Time-Resolved Spectroscopy in High Tc Superconductors

本文研究了室温下ＹＢａ_２Ｃｕ_３Ｏ_（７－ｘ）（ｘ＝０．１，０．４，０．８）和ＰｒＢａ_２Ｃｕ_３Ｏ_（６．９）外延膜的飞秒瞬态反射谱。结果表明，瞬态反射信号△Ｒ（ｔ）的符号和弛豫时间与载流子浓度密切相关，对超导的ＹＢａ_２Ｃｕ_３Ｏ_（６．９），样品进行不同程度的去氧处理或者用Ｒｒ替代Ｙ后，△Ｒ（ｔ）的符号由正变负，弛豫时间由小于１００ｆｓ增加到大于１ｐｓ，说明在高Ｔｃ氧化物超导体中，载流子浓度的减少使载流子－声子耦合强度降低。

Femtosecond time- resolved reflection spectroscopy in high Tc oxide super-conductors YBa_2Cu_3O_(7-x)(x=0.1,0.4,0. 8) and PrBa_2Cu_3O_(6.9) is studied. It is observedthat the signs and the relaxation times of the reflectivity signals △R(t)are related tothe carrier concentration, The signs of △R(t)in YBa_2Cu_3O_(7-x) are found to change frompositive(x=0.1) to negative and the relaxation times are measured to increase fromless than l00 fs to more than 1 ps, with increasing x and with substitution of Pr for Y.These results reveal that the carrier-phonon coupling reduces with the decrease of the carrier concentration.