Kim B S, Kyung W S, Denlinger J D, Kim C, Park S R
Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea.
Center for Correlated Electron Systems, Institute for Basic Science, Seoul, 08826, Korea.
Sci Rep. 2019 Feb 25;9(1):2730. doi: 10.1038/s41598-019-39540-4.
Each plane of layered ReS and ReSe materials has 1D chain structure, from which intriguing properties such as 1D character of the exciton states and linearly polarized photoluminescence originate. However, systematic studies on the 1D character of charge carriers have not been done yet. Here, we report on systematic and comparative studies on the energy-momentum dispersion relationships of layered transition metal dichalcogenides ReS and ReSe by angle resolved photoemission. We found that the valence band maximum or the minimum energy for holes is located at the high symmetric Z-point for both materials. However, the out-of-plane ([Formula: see text]) dispersion for ReSe (20 meV) is found to be much smaller than that of ReS (150 meV). We observe that the effective mass of the hole carriers along the direction perpendicular to the chain is about 4 times larger than that along the chain direction for both ReS and ReSe. Remarkably, the experimentally measured hole effective mass is about twice heavier than that from first principles calculation for ReS although the in-plane anisotropy values from the experiment and calculations are comparable. These observation indicate that bulk ReS and ReSe are unique semiconducting transition metal dichalcogenides having strong one-dimensional characters.
层状ReS和ReSe材料的每个平面都具有一维链状结构，激子态的一维特性和线性偏振光致发光等有趣特性都源于此。然而，尚未对电荷载流子的一维特性进行系统研究。在此，我们报告了通过角分辨光电子能谱对层状过渡金属二硫属化物ReS和ReSe的能量-动量色散关系进行的系统和比较研究。我们发现，两种材料的价带最大值或空穴的最小能量都位于高对称Z点。然而，发现ReSe的面外（[公式：见正文]）色散（20 meV）远小于ReS的（150 meV）。我们观察到，对于ReS和ReSe，沿垂直于链的方向的空穴载流子有效质量约为沿链方向的4倍。值得注意的是，尽管实验和计算得到的面内各向异性值相当，但实验测量的ReS空穴有效质量比第一性原理计算得到的约重两倍。这些观察结果表明，块状ReS和ReSe是具有强一维特性的独特半导体过渡金属二硫属化物。
