无公度Bi2Sr2CaCu2O（8+delta）晶体中长波声子动力学的布里渊光散射光谱研究
Long-wavelength phonon dynamics in incommensurate Bi2Sr2CaCu2O(8+delta) crystals by Brillouin light scattering spectroscopy
摘要：
用布里渊光散射谱研究了高温超导体Bi_2Sr_2CaCu_2O（8+ δ）晶体中的室温声子动力学。八个不同的声学模式进行了观察和鉴定，包括两个准纵向体模和四个准横向体模。在光谱中还观察到在~95 GHz的频移处的峰，其行为使人想起光学声子。这些模式的存在和性质是Bi_2Sr_2CaCu_2 O（8+ δ）的无公度结构的一种表现，并表明它可以被归类为由两个弱相互作用的亚晶格组成的所谓复合无公度晶体。从两个测得的准纵向声速得到的质量比m1/m2=0.36导致亚晶格分配的Bi 2Sr 2 O 4和CaCu 2 O 4。布里渊数据还将公度声子和非公度声子动力学之间的交叉频率的上限设置为~10 GHz。
英文摘要：
Room temperature phonon dynamics in crystals of the high-Tc superconductor Bi2Sr2CaCu2O(8+delta) were probed using Brillouin light scattering spectroscopy. Eight distinct acoustic modes were observed and identified, including two quasi-longitudinal bulk modes and four quasi-transverse bulk modes. A peak at a frequency shift of ~95 GHz with behaviour reminiscent of an optic phonon was also observed in the spectra. The existence and nature of these modes is a manifestation of the incommensurate structure of Bi2Sr2CaCu2O(8+delta) and suggests that it may be categorized as a so-called composite incommensurate crystal comprised of two weakly interacting sublattices. A mass ratio of m1/m2=0.36 obtained from the two measured quasi-longitudinal acoustic velocities led to sublattice assignments of Bi2Sr2O4 and CaCu2O4. The Brillouin data also places an upper limit of ~10 GHz on the crossover frequency between commensurate and incommensurate phonon dynamics.
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