We analyze the one-particle spectral function for the model of Ta₂NiSe₅ by utilizing the functional renormalization group (fRG) method. By properly accounting for one-dimensional fluctuation effects, the scattering process between the fermions in the conduction (c) and valence (f) bands becomes relevant, and there appears a bound state between the c and f fermions without any symmetry breaking in the region where the noninteracting c and f bands overlap. We derive the renormalization group (RG) equation for the self-energy in the functional form, and obtain the explicit k, ω, and T dependencies of the spectral function. We find that the explicit gap structure is obtained in the one-particle spectral function at finite temperatures lower than the characteristic energy scale of the c–f bound state. Based on our detailed analysis, we also report a steep decrease in the density of states at ω = 0, at sufficiently low temperatures. The relevance of our results to the experimental observations for Ta₂NiSe₅ is discussed.

中文翻译：

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一维激子绝缘子谱函数的函数重整化组分析

我们利用功能重整化组（fRG）方法分析了Ta ₂ NiSe ₅模型的单粒子光谱函数。通过适当地考虑一维涨落效应，导带（c）和价带（f）中的费米子之间的散射过程变得相关，并且在该区域中c和f费米子之间出现束缚状态而没有任何对称性破坏非相互作用的c和f波段重叠。我们以函数形式导出自能量的重整化组（RG）方程，并获得显式的k，ω和频谱函数的T相关性。我们发现，在有限的温度下比c - f束缚态的特征能级低的单粒子光谱函数中获得了显式的间隙结构。根据我们的详细分析，我们还报告了在足够低的温度下，ω = 0时状态密度的急剧下降。讨论了我们的结果与Ta ₂ NiSe ₅的实验观察结果的相关性。