Origin of low-energy excitations in charge-ordered manganites
Origin of low-energy excitations in charge-ordered manganites
复制标题
电荷有序亚锰酸盐中低能激发的起源
DOI：
10.1209/0295-5075/90/17005
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
M. Dressel
中科院分区：
文献类型：
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作者：
E. Zhukova;B. Gorshunov;T. Zhang;D. Wu;A. Prokhorov;V. Torgashev;E. Maksimov;M. Dressel
利用频域太赫兹光谱研究了多晶La0.25Ca0.75MnO3中电荷有序相的低能激发。在4 cm−1到700 cm−1的频率范围内（能量从0.4 meV到90 meV），温度低至5 K，我们没有检测到任何与空间调制电荷连续统的集体响应相关的特征。在反铁磁有序相中，宽吸收带出现在电导率和介电常数谱中的30 cm−1和100 cm−1附近，这些吸收带被分配给由于晶格中的四重超结构而被光学激活的前声学声子。我们的研究结果表明，在La 0.25Ca 0.75MnO 3的电荷有序相的集体激发的特征能量，如果有的话，低于1毫电子伏。在我们的最低频率只有几个波数的一个强大的弛豫被观察到100 K以上连接到电荷有序态的形成。
The low-energy excitations in the charge-ordered phase of polycrystalline La0.25Ca0.75MnO3 are explored by frequency-domain terahertz spectroscopy. In the frequency range from 4 cm−1 to 700 cm−1 (energies from 0.4 meV to 90 meV) and at temperatures down to 5 K, we do not detect any feature that can be associated with the collective response of the spatially modulated charge continuum. In the antiferromagnetically ordered phase, broad absorption bands appear in the conductivity and permittivity spectra around 30 cm−1 and 100 cm−1 which are assigned to former acoustic phonons optically activated due to a fourfold superstructure in the crystal lattice. Our results indicate that characteristic energies of collective excitations of the charge-ordered phase in La0.25Ca0.75MnO3, if any, lie below 1 meV. At our lowest frequencies of only few wave numbers a strong relaxation is observed above 100 K connected to the formation of the charge-ordered state.