论文标题
直接观察Ta2nise中激素不稳定5
Direct observation of excitonic instability in Ta2NiSe5
论文作者
论文摘要
狭窄差距半导体或半学的电子和孔之间的库仑吸引力预计将导致一个被称为“激子绝缘子”的物质阶段。但是，对这种电子不稳定性的直接观察仍然极为罕见。在这里，我们报告了使用拉曼光谱法观察到候选材料TA2Nise5的静态激素敏感性中的初始差异。 Critical fluctuations of the excitonic order parameter give rise to quasi-elastic scattering of B2g symmetry, whose intensity grows inversely with temperature toward the Weiss temperature of Tw ~241 K, which is arrested by a structural phase transition driven by an acoustic phonon of the same symmetry at Tc =325 K. Concurrently, a B2g optical phonon becomes heavily damped to the extent that its trace is almost invisible在TC周围，它表现出强烈的电子 - 音波耦合，该耦合掩盖了低温相作为激子绝缘子的识别，已有十多年了。我们的结果明确揭示了相变的电子起源。
Coulomb attraction between electrons and holes in a narrow-gap semiconductor or a semimetal is predicted to lead to an elusive phase of matter dubbed 'excitonic insulator'. However, direct observation of such electronic instability remains extremely rare. Here, we report the observation of incipient divergence in the static excitonic susceptibility of the candidate material Ta2NiSe5 using Raman spectroscopy. Critical fluctuations of the excitonic order parameter give rise to quasi-elastic scattering of B2g symmetry, whose intensity grows inversely with temperature toward the Weiss temperature of Tw ~241 K, which is arrested by a structural phase transition driven by an acoustic phonon of the same symmetry at Tc =325 K. Concurrently, a B2g optical phonon becomes heavily damped to the extent that its trace is almost invisible around Tc, which manifests a strong electron-phonon coupling that has obscured the identification of the low-temperature phase as an excitonic insulator for more than a decade. Our result unambiguously reveals the electronic origin of the phase transition.
