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内耗与超声测量表明在高T_c(100K附近)的超导体YBCO, BSCCO和TBCCO中,在100—300K范围内总存在与晶格参数跳变相关的类相变。与C′=[(C_(11)+C_(22)/2-C_(12)]/2和C_(66)软化有关的铁弹回线总是发生在类相变温区,在某些情况下还观察到形状记忆效应。 对具有不同T_c的BSCCO和TBCCO样品,实验结果表明,在T_c以上存在一个内耗(Q_p~(-1))或超声衰减(α_p)平台,在T_c以下Q_p~(-1)或α_p随温度的降低而明显地减小,但比BCS理论预期的要慢。而对非超导的BiSrCaCuO样品无该种现象出现。该实验结果表明T_c附近的能量损耗反常与超导相变有关。结合Hall效应的测量,表明Q_p~(-1)或超声衰减(α_p)平台与载流子密切相关,该内耗对频率依赖较弱,可用周围具有畸变云的载流子的相关态模型合理地解释。本文在考虑到准粒子的复合效应后,提出了修正的准粒子的跃迁几率,并结合Dynes等提出的准粒子态密度的修正公式,得到了T_c以下内耗的表达式,计算得到的结果和实验结果符合得很好,并且由此而求得的能隙和Γ亦与隧道效应、NMR的结果基本一致。
The results of internal friction and ultrasonic measurements show that in the superconductors YBCO, BSCCO and TBCCO with high Tc (near 100K), there are always the similar phase transitions related to lattice parameter transition in the range of 100-300K. Iron bounce loops associated with C ’= [(C_ (11) + C_ (22) / 2-C_ (12)] / 2 and C_ (66) softening always occur in the quasi-phase- Shape memory effect was also observed.For BSCCO and TBCCO samples with different T_c, the experimental results show that there is a Q_p ~ (-1) or ultrasonic attenuation (α_p) platform above T_c, (-1) or α_p decreases obviously with the decrease of temperature, but it is slower than that predicted by BCS theory. However, this phenomenon does not occur for non-superconducting BiSrCaCuO samples. The experimental results show that the energy loss around T_c is anomalous to Superconducting phase transitions are also observed.The measurement of Hall effect shows that the Q_p ~ (-1) or the ultrasonic decay (α_p) platform is closely related to the carrier, which is weakly dependent on the frequency and can use carriers with distorted clouds around The related state model is reasonably explained.In this paper, the modified quasi-particle transition probability is proposed after considering the complex effect of quasi-particles, and the expression of internal friction below T_c is obtained by combining with the correction formula of quasi-particle state density proposed by Dynes et al The calculated results are in good agreement with the experimental results and the energy gap and Γ obtained therefrom are in good agreement with the tunneling effect , NMR results are basically the same.