Photo-excited dynamics in the excitonic insulator Ta2NiSe5
Photo-excited dynamics in the excitonic insulator Ta2NiSe5
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DOI：
10.1088/1361-648x/aacd76
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发表时间：
2018-08-01
影响因子：
2.7
通讯作者：
Kaiser, Stefan
中科院分区：
文献类型：
--
作者：
Werdehausen, Daniel;Takayama, Tomohiro;Kaiser, Stefan
激子绝缘体是由凝聚激子形成的有趣的相关电子相。一个有希望的候选者是小带隙半导体Ta 2NiSe 5。在这里，我们调查的准粒子和相干声子动力学Ta 2NiSe 5在时间分辨泵浦探测实验。利用Kabanov等人最初为超导体开发的模型（Kabanov等人1999 Phys. Rev. B 59 1497），我们表明，材料的本征能隙在高达约250 K至275 K的温度下几乎与温度无关。这种行为支持Ta 2NiSe 5中激子绝缘体状态的存在。在这些温度以上，对差距的附加温度依赖分量的开始表明材料位于BEC-BCS交叉区域。此外，我们表明，这种状态是非常稳定的，对强的光激发，这表明，自由电荷载流子无法有效地屏蔽电子和空穴之间的吸引库仑相互作用，可能是由于准一维结构的Ta 2NiSe 5。
The excitonic insulator is an intriguing correlated electron phase formed of condensed excitons. A promising candidate is the small band gap semiconductor Ta2NiSe5. Here we investigate the quasiparticle and coherent phonon dynamics in Ta2NiSe5 in a time resolved pump probe experiment. Using the models originally developed by Kabanov el al for superconductors (Kabanov et al 1999 Phys. Rev. B 59 1497), we show that the material's intrinsic gap can be described as almost temperature independent for temperatures up to about 250 K to 275 K. This behavior supports the existence of the excitonic insulator state in Ta2NiSe5. The onset of an additional temperature dependent component to the gap above these temperatures suggests that the material is located in the BEC-BCS crossover regime. Furthermore, we show that this state is very stable against strong photoexcitation, which reveals that the free charge carriers are unable to effectively screen the attractive Coulomb interaction between electrons and holes, likely due to the quasi 1D structure of Ta2NiSe5.