物理化学学报 >> 2018, Vol. 34 >> Issue (12): 1312-1320.doi: 10.3866/PKU.WHXB201803011

所属专题: 表面物理化学

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衬底对N@C60分子电子自旋共振谱的影响

赵烨梁,王兵*()   

  • 收稿日期:2018-01-23 发布日期:2018-04-27
  • 通讯作者: 王兵 E-mail:bwang@ustc.edu.cn
  • 基金资助:
    国家重点研发计划(2016YFA0200603)

Effect of Substrate on the Electron Spin Resonance Spectra of N@C60 Molecules

Yeliang ZHAO,Bing WANG*()   

  • Received:2018-01-23 Published:2018-04-27
  • Contact: Bing WANG E-mail:bwang@ustc.edu.cn
  • Supported by:
    the National Key Research and Development Program of China(2016YFA0200603)

摘要:

N@C60内嵌富勒烯是一种在量子科技领域有较高应用前景的分子。科学家们设计了一系列以内嵌富勒烯分子为基本量子单元的量子计算机模型,而构筑这样的模型具有极高的挑战。其中,由于内嵌富勒烯分子阵列的制备通常需要合适的衬底,而衬底与分子之间的相互作用会影响甚至破坏内嵌N原子的自旋信号。因此研究和理解衬底与内嵌富勒烯分子的相互作用具有重要的意义。本文制备了高质量的N@C60分子,并采用扫描隧道显微镜对其在Au(111)表面的结构及电子态进行表征。通过对比N@C60分子在Au(111)、Si(111)、SiO2表面的电子自旋共振(ESR)信号随时间及其抽真空处理的变化,表明Au原子的核自旋与内嵌N原子的电子自旋的耦合作用是Au(111)表面N@C60单分子层的ESR谱中内嵌N原子的信号衰减的主要原因。

关键词: Au(111), 内嵌富勒烯, 扫描隧道显微镜, 电子自旋共振, 退相干, 偶极耦合

Abstract:

The controlled coupling of spin centers is essential in the construction of molecular spin-based quantum information processing architectures. A major challenge is to induce the requisite coupling between two adjacent spins, while protecting them from neighboring spins and other environmental interactions. Owing to their native spin properties, endohedral fullerenes are attractive for use as elements in quantum information processing architectures. N@C60 is an endohedral fullerene molecule with a highly reactive nitrogen atom at the center of the carbon cage. The endohedral nitrogen is atomic and not covalently bound to the cage atoms; therefore, the nitrogen atom is chemically inert toward the outer environment. Owing to its remarkably long electron-spin lifetimes and sharp resonances, N@C60 has exceptional properties for quantum computing. The thermal stability and molecular structure of N@C60 make it a useful embodiment of a quantum bit — a fundamental element for a quantum computer. Several future quantum computer architectures based on N@C60 have been proposed, one of which is a two-dimensional, quantum-bit array on specific substrates. However, a challenging yet important task is to understand the effect of various substrates on the spin properties of the endohedral fullerene, since the interaction between the endohedral fullerene and the substrate may largely affect the spin characters of the endohedral N atom. The fabrication of an endohedral fullerene molecular array on substrates is also a challenge because high-temperature methods such as evaporation will cause decomposition of N@C60. Here we report our investigation on the electron spin resonance (ESR) of N@C60 molecules on various substrates such as Au(111), Si(111), and SiO2. In this study, N@C60 was prepared using the ion implantation method, and enrichment was performed using a multistep and recycling high-performance liquid chromatography (HPLC) system with a Cosmosil Buckyprep column. N@C60 molecular films on Au(111) substrates were prepared at room temperature. In addition, scanning tunneling microscope (STM) topography of the N@C60/C60 monolayer on Au(111) was obtained at a sample temperature of 5 K in ultra high vacuum (UHV). We found that the ESR signal of the N@C60 molecules decreases rapidly and disappeared approximately 360 min after the deposition of N@C60 on Au(111). In comparison, the ESR signal was maintained for a longer time on the Si(111) and SiO2 substrates. We propose that coupling between the Au(111) substrate and the endohedral N atoms quenches the ESR signal of the endohedral N atom, while the Si(111) and SiO2 substrates have a smaller effect on the ESR signal. This result offers useful information for the design of basic quantum computer architectures.

Key words: Au(111), Endohedral fullerene, Scanning tunneling microscopy, Electron spin Resonance, Decohence, Dipolar coupling

MSC2000: 

  • O647