arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1303.1992cond-mat.str-elcond-mat.mtrl-sci
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过掺杂锰氧化物La_{1-x} Ca_{x} MnO_{3}中的玻色子峰

Boson peak in overdoped manganites La_{1-x}Ca_{x}MnO_{3}

B. Gorshunov, E. Zhukova, V. I. Torgashev, L. S. Kadyrov, L. Motovilova, F. Fischgrabe, V. Moshnyaga T. Zhang, R. Kremer, U. Pracht, S. Zapf, M. Dressel

摘要:

在强掺杂锰氧化物La $_{1-x}$ Ca $_x$ MnO $_3$($x \geq 0.5$)的电荷有序相的吸收线出现在太赫兹光谱范围内的相称的$x$值低于电荷有序温度。它们连接到声学声子,声学声子通过布里渊区的折叠而变得光学活性。在较低的温度下,一个强烈的不对称的额外的吸收带的频率对应的位置的最低能量的范霍夫奇点减少布里渊区。该能带被分配给玻色子峰,即超过标准德拜贡献的晶格振动态的过剩。当没有明显的布里渊区折叠存在时,折叠声子和玻色子峰不显示为无公度的钙含量。

英文摘要:

In the charge-ordered phase of strongly doped manganites La$_{1-x}$Ca$_x$MnO$_3$ ($x \geq 0.5$) absorption lines appear in the terahertz spectral range for commensurate $x$ values right below the charge-ordering temperature. They are connected to acoustic phonons that become optically active by folding of the Brillouin zone. At lower temperatures a strongly asymmetric extra absorption band develops at frequencies corresponding to the position of the lowest-energy van Hove singularity in the reduced Brillouin zone. The band is assigned to the boson peak, i.e. to the excess of lattice vibrational states over the standard Debye contribution. The folded phonons and the boson peak do not show up for incommensurate calcium contents when no distinct Brillouin zone folding exists.

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