非平衡光谱研究激子绝缘相候选材料 Ta_{2}NiSe_{5}中的晶格和电子不稳定性。

Disentangling Lattice and Electronic Instabilities in the Excitonic Insulator Candidate Ta_{2}NiSe_{5} by Nonequilibrium Spectroscopy.

机构信息

Université Paris Cité, CNRS, Matériaux et Phénoménes Quantiques, F-75013 Paris, France.

Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany.

出版信息

Phys Rev Lett. 2023 Mar 10;130(10):106904. doi: 10.1103/PhysRevLett.130.106904.

DOI:10.1103/PhysRevLett.130.106904

PMID:36962049

Abstract

Ta_{2}NiSe_{5} is an excitonic insulator candidate showing the semiconductor or semimetal-to-insulator (SI) transition below T_{c}=326 K. However, since a structural transition accompanies the SI transition, deciphering the role of electronic and lattice degrees of freedom in driving the SI transition has remained controversial. Here, we investigate the photoexcited nonequilibrium state in Ta_{2}NiSe_{5} using pump-probe Raman and photoluminescence spectroscopies. The combined nonequilibrium spectroscopic measurements of the lattice and electronic states reveal the presence of a photoexcited metastable state where the insulating gap is suppressed, but the low-temperature structural distortion is preserved. We conclude that electron correlations play a vital role in the SI transition of Ta_{2}NiSe_{5}.

摘要

Ta_{2}NiSe_{5} 是一种激子绝缘体制备物，在 T_{c}=326K 以下表现出半导体或半金属-绝缘体 (SI) 转变。然而，由于结构转变伴随着 SI 转变，因此电子和晶格自由度在驱动 SI 转变中的作用仍存在争议。在这里，我们使用泵浦-探测拉曼和光致发光光谱法研究了 Ta_{2}NiSe_{5}中的光激发非平衡态。晶格和电子态的组合非平衡光谱测量揭示了存在光激发亚稳态，其中绝缘间隙被抑制，但低温结构畸变得以保留。我们得出结论，电子相关在 Ta_{2}NiSe_{5}的 SI 转变中起着至关重要的作用。