Kondo Effect in Single Atom Contacts: The Importance of the Atomic Geometry

Vitali, Lucia; Ohmann, Robin; Stepanow, Sebastian; Gambardella, Pietro; Tao, Kun; Huang, Renzhong; Stepanyuk, V. S.; Bruno, P.; Kern, Klaus

doi:10.1103/physrevlett.101.216802

Cited by 68 publications

(84 citation statements)

References 29 publications

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“…This leads us to believe that indeed a single impurity determines the zero-bias anomalies. On a small scale, pronounced Kondo phenomena were observed, for example, for tunneling into a single magnetic atom on a metallic surface [19]. But magnetic impurities are not really needed.…”

Section: Discussionmentioning

confidence: 99%

An alternative view at the zero-bias anomaly of metallic point contacts

Gloos

2009

Low Temperature Physics

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We have studied the zero-bias anomaly of point contacts as function of contact size for a wide range of materials from simple normal metals, superconductors, and magnets to highly correlated heavy-fermion compounds. The size dR of the zero-bias anomaly varied in a universal manner proportional to the square of the contact resistance R between 1 W and 10 kW, that is for contact radii from about 15 nm down to 0.2 nm. Magnetic impurities, two-level systems, or a tunneling barrier are unlikely to be the main source of this anomaly. We suggest instead Kondo-type scattering of the conduction electrons due to a spontaneous electron spin polarization at the point contact.

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Section: Discussionmentioning

confidence: 99%

An alternative view at the zero-bias anomaly of metallic point contacts

Gloos

2009

Low Temperature Physics

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“…For Cu-coated W tips all parameters are essentially constant throughout the tunneling, transition and contact ranges in agreement with previous results. 17 Obviously, the chemical identity of the tip apex atom determines the degree of hybridization. The splitting of the resonance due to the magnetic dipole field of the Fe tip at the adatom site is too low to explain the observed broadening.…”

Section: 25mentioning

confidence: 99%

Kondo effect of a Co atom on Cu(111) in contact with an iron tip

2010

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Single Co atoms, which exhibit a Kondo effect on Cu(111), are contacted with Cu and Fe tips in a low-temperature scanning tunneling microscope. With Fe tips, the Kondo effect persists with the Abrikosov-Suhl resonance significantly broadened. In contrast, for Cu-covered W tips, the resonance width remains almost constant throughout the tunneling and contact ranges. The distinct changes of the line width are interpreted in terms of modifications of the Co d state occupation owing to hybridization with the tip apex atoms.

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“…Despite the continuous progress, the electron conductance measured using either a scanning tunneling microscope (STM) or a break-junction device [6][7][8][9][10][11][12][13] has so far not elucidated this question clearly. The strength of the metal-molecule coupling, and in particular its variation during the contact formation, can be characterized through the spectroscopic signal of the molecular vibrations as measured by inelastic electron tunneling spectroscopy (IETS).…”

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confidence: 99%

Surveying Molecular Vibrations during the Formation of Metal−Molecule Nanocontacts

et al. 2010

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Molecular junctions have been characterized to determine the influence of the metal contact formation in the electron transport process through a single molecule. With inelastic electron tunneling spectroscopy and first-principles calculations, the vibration modes of a carbon monoxide molecule have been surveyed as a function of the distance from a copper electrode with unprecedented accuracy. We observe a continuous but nonlinear blue shift of the frustrated rotation mode in tunneling with decreasing distance followed by an abrupt softening upon contact formation. This indicates that the presence of the metal electrode sensibly alters the structural and conductive properties of the junction even without the formation of a strong chemical bond.KEYWORDS Inelastic electron tunneling spectroscopy, electron-vibration coupling, single molecule-metal contact, electron conductance, density functional theory, nonequilibrium Green's function, point contact spectroscopy C harge transport through metal-molecule systems is a major subject of study in a rapidly growing interdisciplinary research field. It deals with fundamental and applied aspects of science at the nanoscale aiming to control the electron conductance at the molecular level and the uprising of nanotechnology.1,2 One of the major results of this research is that the properties of an isolated molecule are not the only fundamental parameters determining the conductance in a metal-molecule junction. Indeed, similarly to the adsorption of molecules on surfaces, the atomistic arrangement at the junction and the coupling between the molecule and the metal electrodes can significantly alter the electronic and structural properties of the molecule.3-5 In particular, the stronger the metal-molecule interaction is, the less the measured conductance can be ascribed to molecular properties alone.Accessing the influence of the molecular contact to the metal in the transport properties is, however, experimentally challenging. Despite the continuous progress, the electron conductance measured using either a scanning tunneling microscope (STM) or a break-junction device 6-13 has so far not elucidated this question clearly. The strength of the metal-molecule coupling, and in particular its variation during the contact formation, can be characterized through the spectroscopic signal of the molecular vibrations as measured by inelastic electron tunneling spectroscopy (IETS). 6,9,[14][15][16][17] This can be recorded as a function of the tip-molecule distance allowing understanding to which extent the contact formation influences the molecular properties.A good molecular prototype to study the influence of the metal bond is carbon monoxide (CO). Indeed, this molecule is used as ligand to contact metal atoms in coordination chemistry and its electronic and vibration properties are very sensitive to the local adsorption environment. Shifts of the vibration frequencies are observed by coadsorption with other gases 18 and explained by subtle mechanisms of charge transfer. 19...

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Kondo Effect in Single Atom Contacts: The Importance of the Atomic Geometry

Cited by 68 publications

References 29 publications

An alternative view at the zero-bias anomaly of metallic point contacts

An alternative view at the zero-bias anomaly of metallic point contacts

Kondo effect of a Co atom on Cu(111) in contact with an iron tip

Surveying Molecular Vibrations during the Formation of Metal−Molecule Nanocontacts

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