THEORETICAL INVESTIGATION OF QUANTUM TRANSPORT PHENOMENA IN AN ATOM BRIDGES CONSTRUCTED BETWEEN AN STM TIP AND A METAL SURFACE

STM 尖端和金属表面之间构建的原子桥中量子输运现象的理论研究

• 批准号: 11640375
• 负责人: KASAI Hideaki
• 金额: $ 2.43万
• 依托单位: Osaka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11640375/
• 关键词: ATOMBRIDGE; NANOWIRE; MAGNETISM; STM; QUANTIZED CONDUCTANCE; VANADIUM; IRON; NICKEL; 第一原理計算; 構造安定性; 量子輸送現象; 電子相関効果; ハバード模型; 強磁性; 走査型トンネル顕微鏡; 金属表面; 原子操作

When a scanning tunneling microscope (STM) tip is brought into contact with a metal surface and then lifted up, an atom-sized contact (point contact) is formed between the tip and the surface. As the tip is further lifted up, by about less than a few nanometers from the surface, an atom-sized wire (a few-atoms across in dimensions) is formed between the STM tip and the metal surface. Because the electrons are confined in the direction normal to the atom bridge axis, the atom bridge exhibits quantized conductance. We have investigated the quantum transport phenomena observable in these atom-sized bridges, made from magnetic materials, using the single-band Hubbard model. We found that, at finite temperatures, because of inter-subband scattering, which originates from the strong electron Coulomb interaction, the corresponding Conductance (G) vs. Length plot shows deviations from the characteristic step-like structure, particularly in the transition region between a conductance plateau an … More d a conductance step. We have also proposed a method on how, using the STM tip, we could manipulate the magnetic and quantum transport properties of these atom bridges. By performing first-principles calculations, we have also determined the possible stable structures for Fe atom bridges, one and two atoms across in dimensions. Furthermore, we have determined how we could control/manipulate the magnetic and quantum transport properties of these atom bridges by changing the composition of the atom wire through alloying and obtain, e.g., atom wires with specific spin polarization ratios of the electric current flowing through them. Consider for example an FeαNi1-α, atom bridge. We found that this alloyed atom bridge exhibits a magnetic moment considerably larger than that predicted by the Pauling-Slater curve for bulk materials. Furthermore, we have determined that the minority spin contribution to the corresponding atom bridge conductance strongly depends on the Ni concentration, although the majority spin contribution remains the same. These properties are determined by the energetic variations in the corresponding s- and d-bands. Thus, a technology based on information gained from this study would provide us with a novel means of designing and realizing functional ballistic spin conductors. Less

当扫描隧道显微镜（STM）尖端与金属表面接触然后抬起时，尖端和表面之间形成原子大小的接触（点接触）。随着尖端进一步提升，距离表面约不到几纳米，STM 尖端和金属表面之间会形成原子大小的线（尺寸为几个原子）。由于电子被限制在垂直于原子桥轴的方向上，因此原子桥表现出量子化电导。我们使用单带哈伯德模型研究了这些由磁性材料制成的原子大小的桥中可观察到的量子输运现象。我们发现，在有限温度下，由于源自强电子库仑相互作用的子带间散射，相应的电导 (G) 与长度图显示出与特征阶梯结构的偏差，特别是在电导平台和电导阶梯之间的过渡区域。我们还提出了一种如何使用 STM 尖端来操纵这些原子桥的磁性和量子传输特性的方法。通过进行第一性原理计算，我们还确定了铁原子桥（一个和两个原子在维度上）可能的稳定结构。此外，我们还确定了如何通过合金化改变原子线的成分来控制/操纵这些原子桥的磁性和量子传输特性，并获得例如具有流经它们的电流的特定自旋极化比的原子线。例如，考虑 FeαNi1-α 原子桥。我们发现这种合金原子桥表现出的磁矩比大块材料的鲍林-斯莱特曲线预测的磁矩大得多。此外，我们已经确定，尽管多数自旋贡献保持不变，但少数自旋对相应原子桥电导的贡献很大程度上取决于 Ni 浓度。这些特性由相应 s 和 d 波段的能量变化决定。因此，基于从这项研究中获得的信息的技术将为我们提供一种设计和实现功能性弹道自旋导体的新方法。较少的

项目成果

Y.Kawahito, H.Kasai, H.Nakanishi, and A.Okiji: "Quantum transport in an atom-sized bridge between a metal surface and a tip of a scanning tunneling microscope at finite temperatures" Journal of Applied Physics. 85. 947-952 (1999)

Y.Kawahito、H.Kasai、H.Nakanishi 和 A.Okiji：“有限温度下金属表面和扫描隧道显微镜尖端之间的原子大小桥中的量子传输”《应用物理学杂志》。

W. A. Dino, H. Kasai and A. Okiji: "H2 dissociation dynamics on an alloy surface-controlling the dynamics via orientation-"Surface Science. 493. 278-284 (2001)

W. A. Dino、H. Kasai 和 A. Okiji：“合金表面上的 H2 解离动力学 - 通过取向控制动力学 -”表面科学。

R. Muhida, W. A. Dino, A. Fukui, H. Kasai, H. Nakanishi, A. Okiji, K. Fukutani and T. Okano: "Molecular orientation dependence of o-p H2 conversion on a 3d impurity sitting on a metal oxide surface"Surface Science. 493. 285-291 (2001)

R. Muhida、W. A. Dino、A. Fukui、H. Kasai、H. Nakanishi、A. Okiji、K. Fukutani 和 T. Okano：“o-p H2 转换对金属氧化物表面上的 3d 杂质的分子取向依赖性”

K. Nobuhara, H. Nakanishi, H, Kasai and A. Okiji: "Behavior of H atom in adsorption states on metal surfaces-localization and delocalization"Surface Science. 493. 271-277 (2001)

K. Nobuhara、H. Nakanishi、H、Kasai 和 A. Okiji：“H 原子在金属表面吸附状态下的行为 - 局域化和离域化”表面科学。

Y. Miura, W. A. Dino, H. Kasai and A. Okiji: "Orientational effects on the molecular diffraction dynamics of Hz scattered from Cu(001)"Surface Science. 482-485. 306-311 (2001)

Y. Miura、W. A. Dino、H. Kasai 和 A. Okiji：“从 Cu(001) 散射的 Hz 分子衍射动力学的方向效应”表面科学。