Inhibition of the photoinduced structural phase transition in the excitonic insulator Ta2NiSe5
Inhibition of the photoinduced structural phase transition in the excitonic insulator Ta2NiSe5
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DOI：
10.1103/physrevb.97.115154
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发表时间：
2018-03-26
影响因子：
3.7
通讯作者：
Staehler, Julia
中科院分区：
文献类型：
--
作者：
Mor, Selene;Herzog, Marc;Staehler, Julia
飞秒时间分辨的中红外反射率是用来调查电子和声子动力学发生在激子绝缘体Ta 2NiSe 5的直接带隙低于其结构相变的临界温度。我们发现，声子动力学表现出很强的耦合，在布里渊区的伽马点的自由载流子的激发。由于光学吸收饱和，光学响应在临界激发通量F-C = 0.30 +/- 0.08 mJ/cm（2）处饱和。这限制了Ta 2NiSe 5中的光激发密度，使得系统不能被足够强地泵浦以经历高温相的结构变化。因此，我们表明，Ta 2NiSe 5表现出阻塞机制时，在近红外区泵浦，防止非热结构相变。
Femtosecond time-resolved midinfrared reflectivity is used to investigate the electron and phonon dynamics occurring at the direct band gap of the excitonic insulator Ta2NiSe5 below the critical temperature of its structural phase transition. We find that the phonon dynamics show a strong coupling to the excitation of free carriers at the Gamma point of the Brillouin zone. The optical response saturates at a critical excitation fluence F-C = 0.30 +/- 0.08 mJ/cm(2) due to optical absorption saturation. This limits the optical excitation density in Ta2NiSe5 so that the system cannot be pumped sufficiently strongly to undergo the structural change to the high-temperature phase. We thereby demonstrate that Ta2NiSe5 exhibits a blocking mechanism when pumped in the near-infrared regime, preventing a nonthermal structural phase transition.