Giant Effects of Interlayer Interaction on Valence-Band Splitting in Transition Metal Dichalcogenides
Giant Effects of Interlayer Interaction on Valence-Band Splitting in Transition Metal Dichalcogenides
复制标题
DOI：
10.1021/acs.jpcc.1c10631
复制
发表时间：
2022-05-13
影响因子：
3.7
通讯作者：
Newaz, Akm
中科院分区：
文献类型：
--
作者：
Benson, Garrett;Costa, Viviane Zurdo;Newaz, Akm
了解过渡金属二硫化物 (TMD) 中价带最大值 (VBM) 分裂的起源非常重要，因为它控制着单层和多层 TMD 中独特的自旋和谷物理。在这项工作中，我们利用光电流光谱系统地研究了原子级薄 MoS2 和 WS2 中的 VBM 分裂 (Delta)。我们发现单层MoS2和WS2中的VBM分裂强烈依赖于温度，这与自旋轨道耦合仅决定单层TMD中VBM分裂的理论相矛盾。我们还发现，VBM 分裂相对于温度的变化率（m = 偏导数 Delta/偏导数 T）对于单层最高（对于 MoS2，为-0.14 meV/K），并且该变化率随着层数的增加而减小（对于 5 层 MOS2，m 近似于 0 meV/K）。我们的密度泛函理论 (DFT) 和 Bethe-Salpeter 方程的 GW (GW-BSE) 模拟与实验观察结果一致，并证明单层和多层 TMD 中 VBM 分裂的温度依赖性源于相邻层和基底之间层间耦合强度的变化。我们还发现 VBM 分裂取决于层数和过渡金属的类型。
Understanding the origin of valence band maxima (VBM) splitting in transition metal dichalcogenides (TMDs) is important because it governs the unique spin and valley physics in monolayer and multilayer TMDs. In this work, we present our systematic study of VBM splitting (Delta) in atomically thin MoS2 and WS2 by employing photocurrent spectroscopy. We found that VBM splitting in monolayer MoS2 and WS2 depends strongly on temperature, which contradicts the theory that spin-orbit coupling solely determines the VBM splitting in a monolayer TMD. We also found that the rate of change of VBM splitting with respect to temperature (m = partial derivative Delta/partial derivative T) is the highest for monolayer (-0.14 meV/K for MoS2) and the rate decreases as the layer number increases (m approximate to 0 meV/K for 5 layers MOS2). Our density functional theory (DFT) and the GW with Bethe-Salpeter Equation (GW-BSE) simulations agree with the experimental observations and demonstrate that the temperature dependence of VBM splitting in monolayer and multilayer TMDs originates from the changes in the interlayer coupling strength between the neighboring layers and substrates. We also found that VBM splitting depends on the layer numbers and the type of transition metals.