论文标题
用谐振X射线散射绘制ta $ _2 $ nise $ _5 $中的空置状态分散体
Mapping the unoccupied state dispersions in Ta$_2$NiSe$_5$ with resonant inelastic x-ray scattering
论文作者
论文摘要
过渡金属硫化金属化型$ _2 $ nise $ _5 $在$ t_c = 328 $ k的二阶过渡涉及一个小晶格失真。低于$ t_c $，其Brillouin区中心的乐队隙增加到约0.35 eV。在这项工作中，我们使用ni $ l_3 $ gedge的谐振非弹性X射线散射（RIX）研究了其低温半导体阶段的TA $ _2 $ _2 $ nise $ _5 $的电子结构。除了弱荧光响应外，我们还观察到我们归因于电子孔激发的强烈拉曼样峰的集合。使用其电子带结构的密度功能理论计算，我们将主要拉曼样峰确定为价和传导带之间的横向过渡。通过执行依赖角度的RIX测量，我们发现了这些电子孔激发的分散，使我们能够提取电子孔连续体的低能边界。根据通过角度分辨光发射光谱测量的价带的分散体，我们得出了最低无占空置传导带的有效质量。
The transition metal chalcogenide Ta$_2$NiSe$_5$ undergoes a second-order phase transition at $T_c=328$ K involving a small lattice distortion. Below $T_c$, a band gap at the center of its Brillouin zone increases up to about 0.35 eV. In this work, we study the electronic structure of Ta$_2$NiSe$_5$ in its low-temperature semiconducting phase, using resonant inelastic x-ray scattering (RIXS) at the Ni $L_3$-edge. In addition to a weak fluorescence response, we observe a collection of intense Raman-like peaks that we attribute to electron-hole excitations. Using density functional theory calculations of its electronic band structure, we identify the main Raman-like peaks as interband transitions between valence and conduction bands. By performing angle-dependent RIXS measurements, we uncover the dispersion of these electron-hole excitations that allows us to extract the low-energy boundary of the electron-hole continuum. From the dispersion of the valence band measured by angle-resolved photoemission spectroscopy, we derive the effective mass of the lowest unoccupied conduction band.
