The ReX₂ system (X = S, Se) exhibits unique properties that differ from other transition metal dichalcogenides. Remarkably, its reduced crystal symmetry results in a complex electronic band structure that confers this material in-plane anisotropic properties. In addition, multilayered ReX₂ presents a strong 2D character even in its bulk form. To fully understand the interlayer interaction in this system, it is necessary to obtain an accurate picture of the electronic band structure. Here, we present an experimental and theoretical study of the electronic band structure of ReS₂ and ReSe₂ at high-hydrostatic pressures. The experiments are performed by photoreflectance spectroscopy and are analyzed in terms of ab initio calculations within the density functional theory. Experimental pressure coefficients for the two most dominant excitonic transitions are obtained and compared with those predicted by the calculations. We assign the transitions to the Z k-point of the Brillouin zone and other k-points located away from high-symmetry points. The origin of the pressure coefficients of the measured direct transitions is discussed in terms of orbital analysis of the electronic structure and van der Waals interlayer interaction. The anisotropic optical properties are studied at high pressure by means of polarization-resolved photoreflectance measurements.

ReX ₂系统（X = S，Se）具有独特的特性，与其他过渡金属二卤化物不同。显着地，其降低的晶体对称性导致复杂的电子能带结构，赋予该材料面内各向异性特性。此外，多层ReX ₂甚至在其本体形式下也具有很强的2D字符。为了充分理解该系统中的层间相互作用，有必要获得电子能带结构的准确图片。在这里，我们介绍了ReS ₂和ReSe ₂的电子能带结构的实验和理论研究。在高静水压力下。实验是通过光反射光谱法进行的，并在密度泛函理论内根据从头算的方式进行了分析。获得了两个最主要的激子跃迁的实验压力系数，并将其与通过计算预测的压力系数进行比较。我们将过渡分配给布里渊区的Z k点和远离高对称点的其他k点。根据对电子结构的轨道分析和范德华层间相互作用，讨论了所测得的直接跃迁的压力系数的来源。借助于偏振分辨光反射率测量，在高压下研究了各向异性光学性能。