Choi Ji-Hae, Jhi Seung-Hoon
Department of Physics, Pohang University of Science and Technology, Cheongam-ro 77, Pohang 37673, Republic of Korea.
J Phys Condens Matter. 2018 Mar 14;30(10):105403. doi: 10.1088/1361-648X/aaac95.
Group-VIIB transition metal dichalcogenides (TMDCs) are known to be stabilized solely in a distorted 1T phase termed as 1T″ phase, which is compared to many stable or metastable phases in other TMDCs. Using first-principles calculations, we study the structural origin of 1T″ phase group-VIIB TMDCs. We find that quasi 1D Peierls-like instability is responsible for the transition to the 1T″ phase ReS monolayer from the 1T' phase, another distorted 1T phase. Two half-filled bands in 1T'-ReS make sharp peaks in the Lindhard function that prompt the charge density wave (CDW) phase with large band gap opening. Our calculations show that overlapping of the two bands in a broad energy range leads to robust CDW phase or stable 1T″ phase in group-VIIB TMDCs against compositional variation, which is in stark contrast to typical Peierls instability driven by a single band. Calculated total energy curve near the critical point exhibits the feature of the first-order Landau transition due to local chemical bonding. The structural stability of the 1T″ phase in group-VIIB TMDCs is thus guaranteed by two half-filled bands and local chemical bonding.
已知VIIB族过渡金属二硫属化物（TMDCs）仅在一种被称为1T″相的扭曲1T相中稳定，这与其他TMDCs中的许多稳定或亚稳相形成对比。我们使用第一性原理计算来研究VIIB族TMDCs的1T″相的结构起源。我们发现类似准一维Peierls的不稳定性是导致从另一种扭曲的1T相即1T'相转变为1T″相ReS单层的原因。1T'-ReS中的两个半填充能带在Lindhard函数中形成尖锐峰值，从而促使具有大能隙打开的电荷密度波（CDW）相出现。我们的计算表明，在较宽能量范围内这两个能带的重叠导致VIIB族TMDCs中出现稳健的CDW相或稳定的1T″相，使其能抵抗成分变化，这与由单个能带驱动的典型Peierls不稳定性形成鲜明对比。在临界点附近计算得到的总能量曲线由于局部化学键合而呈现出一级朗道相变的特征。因此，VIIB族TMDCs中1T″相的结构稳定性由两个半填充能带和局部化学键合保证。
