Centre for Nanoscience and Nanotechnology, Department of Physics, University of Bath, Bath, BA2 7AY, United Kingdom.
Synchrotron SOLEIL, Saint Aubin, and Université Paris-Saclay, BP 48 91192, Gif-sur-Yvette, France.
Sci Rep. 2017 Jul 11;7(1):5145. doi: 10.1038/s41598-017-05361-6.
ReSe and ReS are unusual compounds amongst the layered transition metal dichalcogenides as a result of their low symmetry, with a characteristic in-plane anisotropy due to in-plane rhenium 'chains'. They preserve inversion symmetry independent of the number of layers and, in contrast to more well-known transition metal dichalcogenides, bulk and few-monolayer Re-TMD compounds have been proposed to behave as electronically and vibrational decoupled layers. Here, we probe for the first time the electronic band structure of bulk ReSe by direct nanoscale angle-resolved photoemission spectroscopy. We find a highly anisotropic in- and out-of-plane electronic structure, with the valence band maxima located away from any particular high-symmetry direction. The effective mass doubles its value perpendicular to the Re chains and the interlayer van der Waals coupling generates significant electronic dispersion normal to the layers. Our density functional theory calculations, including spin-orbit effects, are in excellent agreement with these experimental findings.
ReSe 和 ReS 是层状过渡金属二卤化物中较为特殊的化合物，因为它们具有低对称性，并且由于平面内的铼“链”而呈现出各向异性。它们在不依赖于层数的情况下保持着反演对称性，与更为人熟知的过渡金属二卤化物不同，体相和少层 Re-TMD 化合物被认为具有电子和振动解耦的特性。在这里，我们首次通过直接的纳米级角分辨光电子能谱探测到了体相 ReSe 的电子能带结构。我们发现了一种具有高度各向异性的面内和面外电子结构，其中价带最大值并不位于任何特定的高对称方向上。有效质量在垂直于 Re 链的方向上增加了一倍，层间范德华耦合在垂直于层的方向上产生了显著的电子色散。我们的密度泛函理论计算，包括自旋轨道效应，与这些实验结果非常吻合。
