Transient photoinduced 'hidden' phase in a manganite
Transient photoinduced 'hidden' phase in a manganite
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DOI：
10.1038/nmat2929
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发表时间：
2011-02-01
期刊：
影响因子：
41.2
通讯作者：
Koshihara, Shin-ya
中科院分区：
文献类型：
--
作者：
Ichikawa, Hirohiko;Nozawa, Shunsuke;Koshihara, Shin-ya
光致相变在凝聚态物理中特别受关注(1,2)，因为它们可用于在超快时间尺度上改变复杂的宏观材料特性。微观自由度之间的协作相互作用极大地增强了可访问状态的数量和性质，使得以新的方式切换电子、磁性或结构特性成为可能(2-9)。具有电子伏特量级的高能量光子尤其能够进入可能与接近平衡的刺激产生的状态有很大不同的电子状态(10)。在本研究中，我们使用皮秒时间分辨 X 射线衍射报告了电荷和轨道有序 Nd0.5Sr0.5MnO3 薄膜晶格结构的光致变化。光诱导态在结构上是有序的、均匀的、亚稳态的，并且具有不同于任何热力学可达到的状态的晶体学参数。飞秒时间分辨光谱研究表明在这种状态下形成了电子间隙。此外，这种带隙态的类阈值行为和高效率的光生产率凸显了合作相互作用在形成过程中的重要作用。这些综合观察结果表明，存在与迄今为止已知的相图中发现的“隐藏绝缘相”不同的现象。
Photoinduced phase transitions are of special interest in condensed matter physics(1,2) because they can be used to change complex macroscopic material properties on the ultrafast timescale. Cooperative interactions between microscopic degrees of freedom greatly enhance the number and nature of accessible states, making it possible to switch electronic, magnetic or structural properties in new ways(2-9). Photons with high energies, of the order of electron volts, in particular are able to access electronic states that may differ greatly from states produced with stimuli close to equilibrium(10). In this study we report the photoinduced change in the lattice structure of a charge and orbitally ordered Nd0.5Sr0.5MnO3 thin film using picosecond time-resolved X-ray diffraction. The photoinduced state is structurally ordered, homogeneous, metastable and has crystallographic parameters different from any thermodynamically accessible state. A femtosecond time-resolved spectroscopic study shows the formation of an electronic gap in this state. In addition, the threshold-like behaviour and high efficiency in photo-generation yield of this gapped state highlight the important role of cooperative interactions in the formation process. These combined observations point towards a 'hidden insulating phase' distinct from that found in the hitherto known phase diagram.