Whitcher T J, Fauzi Angga Dito, Caozheng D, Chi X, Syahroni A, Asmara T C, Breese M B H, Neto A H Castro, Wee A T S, Majidi M Aziz, Rusydi A
Advanced Research Initiative for Correlated-Electron Systems (ARiCES), Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117576, Singapore.
Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore, 117603, Singapore.
Nat Commun. 2021 Nov 30;12(1):6980. doi: 10.1038/s41467-021-27182-y.
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.
电子关联在凝聚态物理中驱动奇异现象方面发挥着重要作用。它们通过远超出光学范围的高能带来决定低能性质。人们已经做出了巨大努力来理解低能激发，比如过渡金属二硫属化物（TMDCs）中的低能激子，然而它们的高能带和层间关联仍然是个谜。在此，通过测量块状二硫化钼从近红外到软X射线的温度和偏振相关的复介电常数和损耗函数，并辅以理论计算，我们发现了具有低损耗的非常规软X射线关联等离子体激元，以及降低维度并增强关联的电子跃迁，同时伴随着低能激子的显著改变。在室温下，层间电子关联与c轴方向的层内关联出奇地强，形成了类似三维的体系。冷却时，几十电子伏特范围内会发生大范围的光谱权重转移，面内p-d杂化增强，揭示出强库仑关联和电子各向异性，形成了类似二维的体系。我们的结果表明了强电子、层间和层内关联在决定电子结构方面的重要性，并为在等离子体纳米光刻中利用TMDCs开辟了应用前景。
