Electronic correlations play important roles in driving exotic phenomena in condensed matter physics. They determine low-energy properties through high-energy bands well-beyond optics. Great effort has been made to understand low-energy excitations such as low-energy excitons in transition metal dichalcogenides (TMDCs), however their high-energy bands and interlayer correlation remain mysteries. Herewith, by measuring temperature- and polarization-dependent complex dielectric and loss functions of bulk molybdenum disulphide from near-infrared to soft X-ray, supported with theoretical calculations, we discover unconventional soft X-ray correlated-plasmons with low-loss, and electronic transitions that reduce dimensionality and increase correlations, accompanied with significantly modified low-energy excitons. At room temperature, interlayer electronic correlations, together with the intralayer correlations in the c-axis, are surprisingly strong, yielding a three-dimensional-like system. Upon cooling, wide-range spectral-weight transfer occurs across a few tens of eV and in-plane p–d hybridizations become enhanced, revealing strong Coulomb correlations and electronic anisotropy, yielding a two-dimensional-like system. Our result shows the importance of strong electronic, interlayer and intralayer correlations in determining electronic structure and opens up applications of utilizing TMDCs on plasmonic nanolithrography.

电子相关性在驱动凝聚态物理中的奇异现象方面发挥着重要作用。他们通过远远超出光学范围的高能带确定低能特性。人们为理解低能激发（例如过渡金属二硫属化物（TMDC）中的低能激子）付出了巨大的努力，但它们的高能带和层间相关性仍然是个谜。因此，通过测量从近红外到软X射线的块状二硫化钼的温度和偏振相关的复杂介电常数和损耗函数，并在理论计算的支持下，我们发现了具有低损耗的非常规软X射线相关等离子体激元，并且降低维度并增加相关性的电子跃迁，伴随着显着修改的低能激子。在室温下，层间电子相关性以及c轴的层内相关性非常强，产生了类似三维的系统。冷却后，在几十电子伏特范围内发生宽范围的光谱权重转移，面内p-d杂化增强，揭示出强库仑相关性和电子各向异性，产生类似二维的系统。我们的结果表明了强电子、层间和层内相关性在确定电子结构中的重要性，并开辟了在等离子体纳米光刻中利用 TMDC 的应用。