Reduction of the Superconducting Gap of Ultrathin Pb Islands Grown on Si(111)

Brun, Christophe; Hong, I-Po; Patthey, F.; Sklyadneva, I. Yu.; Heid, R.; Echenique, Pedro M.; Bohnen, K.‐P.; Chulkov, Eugene V.; Schneider, W. D.

doi:10.1103/physrevlett.102.207002

Cited by 141 publications

(166 citation statements)

References 33 publications

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“…So, for the experiments reported in Ref. 9, g is not sensitive to the change of Si(111) surface crystal ordering from (7 × 7) to ( Note that the first and second data-sets in the present study were considered in our previous work. 2 However, in that paper we performed time consuming calculations invoking the full BdG formalism.…”

Section: B Impact Of the Thickness-dependent Coupling Between Electronsmentioning

confidence: 98%

“…The critical temperature of atomically flat Pb nanofilms with thickness down to a few monolayers on a Si(111) substrate have been measured under different conditions. [3][4][5][6][8][9][10] It was found that superconductivity is not destroyed by fluctuations even when the thickness of the nanofilm is only a single monolayer, 10 and the dependence of the critical temperature on thickness shows oscillations with a period close to two monolayers (ML), 3,5 i.e., the even-odd staggering in the superconducting properties.…”

Section: Introductionmentioning

confidence: 99%

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Superconducting transition temperature of Pb nanofilms: Impact of thickness-dependent oscillations of the phonon-mediated electron-electron coupling

Chen¹,

Shanenko²,

Peeters³

2012

Phys. Rev. B

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To date, several experimental groups reported measurements of the thickness dependence of Tc of atomically uniform single-crystalline Pb nanofilms. The reported amplitude of the Tc-oscillations varies significantly from one experiment to another. Here we propose that the reason for this unresolved issue is an interplay of the quantum-size variations in the single-electron density of states with thickness-dependent oscillations in the phonon mediated electron-electron coupling. Such oscillations in the coupling depend on the substrate material, the quality of the interface, the protection cover and other details of the fabrication process, changing from one experiment to another. This explains why the available data do not exhibit one-voice consistency about the amplitude of the Tc-oscillations. Our analyses are based on a numerical solution of the Bogoliubovde Gennes equations for a superconducting slab.

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Section: B Impact Of the Thickness-dependent Coupling Between Electronsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Superconducting transition temperature of Pb nanofilms: Impact of thickness-dependent oscillations of the phonon-mediated electron-electron coupling

Chen¹,

Shanenko²,

Peeters³

2012

Phys. Rev. B

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“…However, the rich variety of unexpected phenomena which were observed has incited research also in temperature ranges far above the superconduction transition temperature T C of Pb. Examples of these observations are the strong dependence of the Schottky barrier on the exact atomic structure 6 , the formation of magic height islands 7 , anomalies in the superconductivity transition temperature [8][9][10] , oscillations of the work function and extremely long excited state life times 11,12 , and the observation of a Rashba-type spin splitting 13 . The origin of many of these phenomena lies in the peculiar electronic structure of Pb on Si(111) manifested in the high in-plane effective mass [14][15][16] .…”

Section: Introductionmentioning

confidence: 99%

Controlling the effective mass of quantum well states in Pb/Si(111) by interface engineering

et al. 2011

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The in-plane effective mass of quantum well states in thin Pb films on a Bi reconstructed Si (111) surface is studied by angle-resolved photoemission spectroscopy. It is found that this effective mass is a factor of 3 lower than the unusually high values reported for Pb films grown on a Pb reconstructed Si(111) surface. Through a quantitative low-energy electron diffraction analysis the change in effective mass as a function of coverage and for the different interfaces is linked to a change of about 2% in the in-plane lattice constant. To corroborate this correlation, density functional theory calculations are performed on freestanding Pb slabs with different in-plane lattice constants. These calculations show an anomalous dependence of the effective mass on the lattice constant including a change of sign for values close to the lattice constant of Si(111). This unexpected relation is due to a combination of reduced orbital overlap of the 6pz states and altered hybridization between the 6pz and the 6pxy derived quantum well states. Furthermore, it is shown by core-level spectroscopy that the Pb films are structurally and temporally stable at temperatures below 100 K. Controlling the effective mass of quantum well states in Pb/Si(111) by interface engineering The in-plane effective mass of quantum well states in thin Pb films on a Bi reconstructed Si(111) surface is studied by angle-resolved photoemission spectroscopy. It is found that this effective mass is a factor of three lower than the unusually high values reported for Pb films grown on a Pb reconstructed Si(111) surface. Through a quantitative low-energy electron diffraction analysis the change in effective mass as a function of coverage and for the different interfaces is linked to a change of around 2 % in the in-plane lattice constant. To corroborate this correlation, density functional theory calculations were performed on freestanding Pb slabs with different in-plane lattice constants. These calculations show an anomalous dependence of the effective mass on the lattice constant including a change of sign for values close to the lattice constant of Si(111). This unexpected relation is due to a combination of reduced orbital overlap of the 6pz states and altered hybridization between the 6pz and 6pxy derived quantum well states. Furthermore it is shown by core level spectroscopy that the Pb films are structurally and temporally stable at temperatures below 100 K.

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“…[5][6][7][8] Since for semiconductor heterostructures with ultralow electron concentrations Fermi wavelengths can be of the order of 100 nm, size quantization or Coulomb blockade ͑CB͒ effects are comparably easy to observe in these systems at low temperature. Consequently, the detailed structure of interfaces and defects on the atomic scale are only of minor relevance and, thus, ͑Ohmic͒ contacts for transport studies are well defined on this length scale.…”

Section: Introductionmentioning

confidence: 99%

Coulomb blockade effects in Ag/Si(111): The role of the wetting layer

2009

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Single and double barrier structures have been realized with Ag nanostructures grown on Si͑111͒ in combination with scanning tunneling microscopy. The series connection of a Schottky ͑SB͒ and tunneling barrier mimics a double barrier structure showing Coulomb blockade oscillations as revealed by scanning tunneling spectroscopy ͑STS͒. Although the SB remains in presence of a Ag ͱ 3 ϫ ͱ 3 reconstruction, the dI / dV characteristic turns into a single barrier structure. The Ag reconstruction provides a sufficiently high electron mobility capturing intrinsic defects which shortens the resistance of the SB. These results show that vertical transport properties, as measured with STS, are not only controlled by the structure and the bonding on the atomic scale, but depend strongly on the lateral properties of the interface as well.

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Reduction of the Superconducting Gap of Ultrathin Pb Islands Grown on Si(111)

Cited by 141 publications

References 33 publications

Superconducting transition temperature of Pb nanofilms: Impact of thickness-dependent oscillations of the phonon-mediated electron-electron coupling

Superconducting transition temperature of Pb nanofilms: Impact of thickness-dependent oscillations of the phonon-mediated electron-electron coupling

Controlling the effective mass of quantum well states in Pb/Si(111) by interface engineering

Coulomb blockade effects in Ag/Si(111): The role of the wetting layer

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