电子型掺杂高温超导体La_(2-x)Ce_xCuO_4飞秒时间分辨动力学研究  

Femtosecond time-resolved dynamics in electron-doped high-T_c superconductor La_(2-x)Ce_xCuO_4

作　　者：曹宁[1] 龙拥兵[1] 张治国[1] 高丽娟[1] 袁洁[1] 赵伯儒[1] 赵士平[1] 杨乾生[1] 赵继民[1] 傅盘铭[1] 

机构地区：[1]中国科学院物理研究所北京凝聚态物理国家实验室,北京100080

出　　处：《物理学报》2008年第4期2543-2547,共5页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:10574155)资助的课题~~

摘　　要：利用飞秒时间分辨光抽运探测技术研究了电子型掺杂La2-xCexCuO4(LCCO)高温超导材料的准粒子超快动力学过程.得到低温(T<0.7Tc)、转变温度附近(0.7Tc≤T≤Tc)和高温(T>Tc)三个温区内的动力学行为.研究发现,低温时准粒子寿命随温度上升而下降,接近转变温度时出现反常的上升,正常态准粒子寿命受赝能隙影响明显大于金属中电声子的弛豫时间.还发现电子型掺杂LCCO光感生反射率变化ΔR/R动力学曲线存在皮秒量级的上升过程,它反映Cooper对被打散的时间较长,上升时间随温度增加而变短.采用Rothwarf和Taylar提出的理论模型对实验结果进行了分析.The quasiparticle dynamics in the electron-doped high-Tc superconductor La2- x Cex CuO4 （LCCO） was investigated by uhrafast time-resolved optical pump-probe technique. We present results in three temperature regions： namely the low temperature （T〈0.7Tc） region, that around Tc（0.7Tc≤ T≤ Tc） and the high temperature （T 〉 Tc） region. In general, there was a slowdown of the relaxation as the temperature decreases. However, the quasiparticle lifetime was found to exhibit a quasi-divergence as the temperature approached Te from below. The relaxation time in normal state was much longer than what was expected for metallic relaxation, indicating the presence of a T-independent pseudogap. We have also observed picosecond rise component of photoinduced change in reflectivity AR/R in the electron-doped LCCO, which is attributed to the Cooper pairbreaking dynamics. The rise time became shorter as the temperature increased. The experimental results are analyzed by Rothwarf-Taylor model.

关 键 词：电子型掺杂高温超导体 飞秒时间分辨 准粒子 声子瓶颈 

分 类 号：O511[理学—低温物理]