Ultrafast dephasing of coherent optical phonons in atomically controlled GeTe/Sb2Te3 superlattices
Ultrafast dephasing of coherent optical phonons in atomically controlled GeTe/Sb2Te3 superlattices
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DOI：
10.1103/physrevb.79.174112
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发表时间：
2009-05
影响因子：
3.7
通讯作者：
M. Hase;Yoshinobu Miyamoto;J. Tominaga
中科院分区：
文献类型：
--
作者：
M. Hase;Yoshinobu Miyamoto;J. Tominaga
利用反射型泵浦探测技术，研究了具有三种不同态的半导体超晶格（SLs）中$\text{GeTe}/{\text{Sb}}_{2}{\text{Te}}_{3}$超晶格中相干光学声子的飞秒动力学。在生长的SLs中获得的时间分辨瞬态反射率在5.10和3.78太赫兹处表现出相干的${\text{A}}_{1}$光学模式，而在退火SLs中只观察到3.68太赫兹处的单一的${\text{A}}_{1}$模式。退火SLs中${\text{A}}_{1}$模式的衰减率与温度密切相关，而生长SLs中的衰减率与温度无关。结果表明，非晶SLs中相干${\text{A}}_{1}$声子的阻尼是由声子-缺陷（空位）散射而不是非谐波声子-声子耦合控制的。
Femtosecond dynamics of coherent optical phonons in $\text{GeTe}/{\text{Sb}}_{2}{\text{Te}}_{3}$ superlattices (SLs), a new class of semiconductor SLs with three different states, have been investigated by using a reflection-type pump-probe technique at various lattice temperatures. The time-resolved transient reflectivity obtained in as-grown SLs exhibits the coherent ${\text{A}}_{1}$ optical modes at 5.10 and 3.78 THz while only the single ${\text{A}}_{1}$ mode at 3.68 THz is observed in annealed SLs. The decay rate of the ${\text{A}}_{1}$ mode in annealed SLs is strongly temperature dependent while that in as-grown SLs is not temperature dependent. This result indicates that the damping of the coherent ${\text{A}}_{1}$ phonons in amorphous SLs is governed by the phonon-defect (vacancy) scattering rather than the anharmonic phonon-phonon coupling.