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，在尖端和表面之间形成原子大小的接触（点接触）。随着尖端进一步抬起，从表面较少的纳米少于几纳米，在STM尖端和金属表面之间形成了原子尺寸的电线（横跨尺寸的几个原子）。由于电子限制在与原子桥轴正常的方向上，因此原子桥表现出量化的电导。我们已经研究了使用单频段哈伯德模型在这些原子大小的桥中观察到的量子传输现象。我们发现，在有限的温度下，由于子带间散射，源自强的电子库仑相互作用，相应的电导率（g）与长度图显示了与特征阶梯状结构的偏差，尤其是在电导率高原之间的过渡区域，并且是电导率的多个电导步骤。我们还提出了一种方法，即使用STM尖端如何操纵这些原子桥的磁和量子传输特性。通过执行第一原理计算，我们还确定了Fe Atom Bridges，一个和两个原子的稳定结构。此外，我们已经确定了如何通过将原子电线的组成通过合金和获得，例如具有特定的电流流动电流的特定自旋极化比的原子电线来控制这些原子桥的磁和量子传输特性。例如，考虑一个FEαNI1-α，原子桥。我们发现，这座合金的原子桥表现出一个磁力时刻，该磁力力矩比鲍林 - 莱特曲线对散装材料预测的磁矩要大。此外，我们确定对相应原子桥电导的少数自旋贡献很大程度上取决于Ni浓度，尽管大多数自​​旋贡献保持不变。这些特性取决于相应的S和D波段中的能量变化。这是一项基于从这项研究中获得的信息的技术，将为我们提供一种新颖的设计和实现功能性弹道旋转导体的方法。较少的

项目成果

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。

Kasai Hideaki: "Behavior of a Magnetic Atom on a Metal Surface-Real Space Image of the Kondo Effect"Journal of Electron Spectroscopy and Related Phenomena. (予定).

葛西英明：“磁性原子在金属表面上的行为-近藤效应的真实空间图像”电子光谱学及相关现象杂志（计划中）。

K. Nobuhara, H. Nakanishi, H. Kasai and A. Okiji: "Quantum mechanical behavior of an H atom on Cu(111) and Pt(111)"Journal of Applied Physics. 91. 1855-1859 (2002)

K. Nobuhara、H. Nakanishi、H. Kasai 和 A. Okiji：“Cu(111) 和 Pt(111) 上 H 原子的量子力学行为”应用物理学杂志。