A time-dependent order parameter for ultrafast photoinduced phase transitions
A time-dependent order parameter for ultrafast photoinduced phase transitions
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DOI：
10.1038/nmat4046
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发表时间：
2014-10-01
期刊：
影响因子：
41.2
通讯作者：
Staub, U.
中科院分区：
文献类型：
--
作者：
Beaud, P.;Caviezel, A.;Staub, U.
强关联电子系统通常在结构自由度和电子自由度之间表现出非常强的相互作用，导致复杂和有趣的相图（1，2）。对于这些材料的技术应用，重要的是要了解如何驱动从一个阶段到另一个阶段的转变。这里的一个关键问题是这种相变的最终速度，以及了解相变如何在时域中演变（3-13）。在这里，我们应用时间分辨X射线衍射直接测量的变化，在超快熔化的电荷和轨道有序相在钙钛矿锰氧化物的长程有序。我们发现，虽然与此过渡相关的晶体对称性的实际变化发生在不同的时间尺度特性的许多电子和振动坐标的系统，相变的动力学可以很好地描述使用一个单一的时间依赖的“序参数”，完全依赖于电子激发。
Strongly correlated electron systems often exhibit very strong interactions between structural and electronic degrees of freedom that lead to complex and interesting phase diagrams(1,2). For technological applications of these materials it is important to learn how to drive transitions from one phase to another. A key question here is the ultimate speed of such phase transitions, and to understand how a phase transition evolves in the time domain(3-13). Here we apply time-resolved X-ray diffraction to directly measure the changes in long-range order during ultrafast melting of the charge and orbitally ordered phase in a perovskite manganite. We find that although the actual change in crystal symmetry associated with this transition occurs over different timescales characteristic of the many electronic and vibrational coordinates of the system, the dynamics of the phase transformation can be well described using a single time-dependent 'order parameter' that depends exclusively on the electronic excitation.