Unveiling Metal-Cage Hybrid States in a Single Endohedral Metallofullerene

Abstract

The local structural and electronic properties of individual metallofullerenes are studied using scanning tunneling microscopy, scanning tunneling spectroscopy, and theoretical simulations. The energy-resolved metal-cage hybrid states of a single endohedral metallofullerene Dy@C 82 isomer I have been spatially mapped, supporting a complex picture consisting of the orbital hybridization and charge transfer for the interaction between the cage and the metal atom. The relative position of the encapsulated Dy atom inside the cage and the molecular orientation on the surface have been inferred by comparing the experimental results with theoretical simulations. The combined technique provides promising applications in the fields of in situ characterization and diagnostics of metallofullerene-based nanodevices. DOI: 10.1103/PhysRevLett.91.185504 PACS numbers: 61.48.+c, 31.15.Ew, 68.37.Ef, 73.22.-f Endohedral metallofullerenes have been a subject of intensive investigation in recent years, not only because of their structural and electronic novelties but also because of their promising electronic, optical, and biomedical applications [1]. The location of metal atoms inside the fullerene cage and the metal-cage interaction are two central issues. Various diffraction, spectroscopy, and microscopy techniques have been used to characterize metallofullerenes [2][3][4][5][6][7]. Most of them require macroscopic quantities of metallofullerenes and give either ensemble averaged or spatially averaged results. It has been a challenging task to characterize the local properties of isolated metallofullerene molecules [8][9][10][11]. Here we show that scanning tunneling microscopy (STM) can be used to detect the encapsulated metal atom inside a fullerene cage. The energy-resolved metal-cage hybrid states of a single endohedral metallofullerene Dy@C 82 isomer I have been spatially mapped using scanning tunneling spectroscopy (STS). Compared with other states of the metallofullerene, these hybrid states provide unique information on the location of metal atoms inside the fullerene cage and the metal-cage interaction. The relative position of the encapsulated Dy atom inside the cage and the molecular orientation on the surface have been inferred by comparing the experiments with theoretical simulations.The Dy@C 82 isomer I is a metallofullerene in which the Dy atom lies along a C 2 axis on the six-membered ring of the C 2v -C 82 cage [6]. Details for the preparation and separation of Dy@C 82 isomer I were described elsewhere [12,13]. A small amount of solid powder of Dy@C 82 was obtained in a crucible by evaporation of solvent in a dry box. The experiments were conducted in an ultrahigh vacuum STM chamber with a base pressure of 3 10 ÿ11 Torr. We first evaporated one monolayer Ag onto a Si(111) surface to form a 3 p 3 p -Ag surface and then a submonolayer of Dy@C 82 molecules was deposited on the Ag surface. All STM and STS measurements were performed at 5 K using an OMICRON cryostat GmbH STM with W tips that had been subject to ca...

Structural and electronic properties of Gd@C60: All-electron relativistic total-energy study

“…On the other hand, the lowest unoccupied Gd 5d derived molecular orbital has some component on C 60 . The orbital hybridization between the guest transition metal (and lanthanide) atoms and fullerene is another common character in metallofullerenes [15][16][17][18] in addition to the charge transfer, and accounts for the nonzero population on the Gd 6s-dominated orbital.…”

UHV-STM/STS Studies of Endohedral La-Metallofullerenes on Hydrogen Terminated Si(100)2×1

“…Cage structures of the fullerenes and properties of encapsulated metal atoms of various endohedral metallofullerenes play important roles for determining the electronic properties of endohedral metallofullerenes. Scanning tunneling microscopy/spectroscopy (STM/STS) is a useful method to directly image the structures and electronic properties of fullerenes and endohedral metallofullerenes with an atomic resolution and a number of STM studies have previously been performed to characterize fullerenes on various surfaces [2][3][4][5][6][7]. In this letter, we report structures and electronic properties of La 2 @C 80 , La@C 82 and La 2 @C 72 molecules in monolayer and multi-layer islands grown on a hydrogen terminated Si(100)-2×1 surface by using an UHV-STM.…”

Parity-based mirror inversion for efficient quantum state transfer and computation in nearest-neighbor arrays

“…Many proposed implementations for a physical quantum computer use a one-dimensional line of qubits with nearestneighbor (NN) interactions [1][2][3][4][5][6][7][8][9][10][11], called linear nearestneighbor (LNN) arrays, where a qubit interacts only with the two qubits adjacent to it. As such, to perform an operation between two remote qubits along the array, that is, between qubits that are not nearest neighbors, often additional SWAP gate operations are required to first bring the qubits adjacent to each other.…”