超强Au-Te键导致金上单层ZrTe$_5$的无序化
Ultrastrong Au-Te bonding drives disorder in monolayer ZrTe$_5$ on gold
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- Hungarian Research Network, HUN-REN Centre for Energy Research, Institute of Technical Physics and Materials Science（匈牙利研究网络，HUN-REN能源研究中心，技术物理与材料科学研究所）
- MTA - HUN-REN EK Lendület “Momentum” Topology in Nanomaterials Research Group（MTA-HUN-REN EK Lendulet“动量”纳米材料拓扑研究组）
- Budapest University of Technology and Economics（布达佩斯技术与经济大学）
- ELTE Eötvös Loránd University（罗兰大学）
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中文总结 AI 辅助
本研究通过实验与计算发现，金辅助剥离的单层ZrTe$_5$因强Te-Au化学吸附破坏层内Te-Te键而呈现无序，阻碍量子自旋霍尔相，而厚层保持有序结构。
中文摘要 AI 辅助
单层ZrTe$_5$被预测具有大带隙量子自旋霍尔相，这促使人们努力分离该材料的单层。金辅助剥离可产生许多以硫族元素封端的范德华晶体的干净单层，但强的Te-Au键可能与ZrTe$_5$层自身的键合网络竞争。在数十个样品中，对金剥离薄片的低温扫描隧道显微镜显示，在绝大多数情况下，单层表面呈无序状态，而较厚的薄片则保留了特征性的准一维链状结构。ZrTe$_5$/Au(111)界面的从头计算再现了这种不对称性并阐明了其机制：面向金的Te原子发生化学吸附，破坏了连接ZrTe$_3$链的弱锯齿形Te-Te键，将晶体离散的键长谱转变为连续谱，而链则作为扭曲单元存续。电荷分析显示了共价Te-Au键的特征，伴随着适度的电荷转移，对单层进行空穴掺杂；在双层中，畸变和掺杂仅限于与金接触的层，而化学吸附和无序均阻碍了所预测的量子自旋霍尔相。相同的准共价Te-Au键可能扰动其他金剥离的Te封端晶体的接触层，尤其是那些具有弱连接的层内网络的晶体。
英文摘要
Monolayer ZrTe$_5$ is predicted to host a large-gap quantum spin Hall phase, motivating efforts to isolate single layers of the material. Gold-assisted exfoliation produces clean monolayers of many chalcogen-terminated van der Waals crystals, but the strong Te-Au bond may compete with the bonding network of the ZrTe$_5$ layer itself. Across tens of samples, low-temperature scanning tunneling microscopy on gold-exfoliated flakes shows a disordered monolayer surface in the overwhelming majority of cases, while thicker flakes preserve the characteristic quasi-one-dimensional chain structure. \emph{Ab initio} calculations of the ZrTe$_5$/Au(111) interface reproduce this asymmetry and resolve its mechanism: the Te atoms facing the gold chemisorb, rupturing the weak zigzag Te-Te bonds that cross-link the ZrTe$_3$ chains, turning the discrete bond-length spectrum of the crystal into a continuous one, while the chains persist as distorted units. Charge analysis shows the signature of covalent Te-Au bonding with a modest transfer that hole-dopes the monolayer; in the bilayer, the distortion and the doping stay confined to the layer contacting the gold, and the chemisorption and disorder each preclude the predicted quantum spin Hall phase. The same quasi-covalent Te-Au bond may perturb the contact layer of other gold-exfoliated Te-terminated crystals, particularly those with weakly connected intralayer networks.
