Phonon structure in the tunneling characteristics of thin proximity effect sandwiches

Chaikin, P. M.; Arnold, G.; Hansma, P. K.

doi:10.1007/bf00654570

Cited by 58 publications

(13 citation statements)

References 31 publications

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“…As summarized in Tables I and II, for the reference 3D-metals in the weak to strong EPC region, we can obtain reasonable values in both the EPC constants and resistivities when compared with the other DFT not using the US-PPs and experimental data [5,6,[28][29][30], indicating the validity of the present calculated a 2 tr F(x) and a 2 sc F(x). In addition, the calculated ab-plane resistivities for one of the typical anisotropic metals without the charge density wave (CDW) transition, pseudo-2D 2H-NbS 2 are also consistent with the experimental data [31,32].…”

Section: Resultssupporting

confidence: 63%

Transport properties of two‐dimensionally fused zinc porphyrins from linear‐response approach

Yamaguchi¹

2010

Int J of Quantum Chemistry

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Transport properties, temperature-dependent phonon-limited electrical and thermal resistivities in the normal state of two-dimensionally (2D) infinite-fused zinc porphyrin with a directly meso-meso-, b-b-, and b-b-linked array structure ZnP 1 were theoretically calculated using linear-response approach based on density functional theory (DFT). The calculated transport electron-phonon coupling (EPC) constant using the density functional perturbation theory (DFPT) shows almost equal to the superconducting EPC constant, which is the similar situation within a difference by ca. 10% between them for the transition metals. The calculated electrical and thermal resistivities at 300 K obtained by solving the Boltzmann equation within the lowestorder variational approximation (LOVA) are only larger by one digit than those of the reference metal Al, expecting to become a fantastic 2D synthetic metal without an injection of conductive carriers from outside, e.g., by doping. The calculated results for the 2D infinite-fused lithium porphyrin LiP 1 with the same ground state as the oneelectron oxidative state of ZnP 1 were also discussed for comparison. This simple approach using the first applied plane-wave ultrasoft pseudopotentials (US-PPs) is a usable technique for the prediction of the transport properties of simple metallic materials within the practical temperature range.

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Section: Resultssupporting

confidence: 63%

Transport properties of two‐dimensionally fused zinc porphyrins from linear‐response approach

Yamaguchi¹

2010

Int J of Quantum Chemistry

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“…Nonetheless, if we blindly use the method described in Ref. 13 for all of the junctions we have studied, we obtain h = 0.11 + 0.03 for Cu, in agreement with the value obtained in that reference. The agreement emphasizes the dominant role played by h in determining the amplitude of the phonon structure observed.…”

Section: F(y)= F~ ~ ~Xy)supporting

confidence: 75%

“…The induced gap (f~N) variation due only to changes in dN is indicated by large dots and that due to the contaminated Cu-Pb interface by points in squares.To within a logarithmic correction, Eq. (24) from Ref 13. gives the relationwas derived from the Eliashberg gap equation for an electronphonon matrix element a and a phonon density of states of Lorentzian form centered about wN and of width bN.…”

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confidence: 99%

Tunneling investigation of Cu-Pb proximity sandwiches. Barrier transmission effects

Wilson

Chaikin

1980

J Low Temp Phys

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We have measured the tunneling characteristics (I, dV/dI, and dZV/dI 2 vs. voltage) for a series or junctions of the form Al-Ox-Cu-Pb for Cu thicknesses ranging from 400 to 3000 ~. From the second derivative characteristics we obser~c two distinct contributions, one from an electron interference effect and another from the interaction of the superconducting electrons with phonons in the Cu. These contributions may be separated by the application of a magnetic field less than the critical field of the sandwich. The electron interference effect provides a direct measurement of the Fermi velocity in the normal metal, while the interactions with the Cu phonons provide a measurement of the electronphonon coupling constant. Contamination of the interface between Cu and Pb by oxidation of the Cu allows us to decouple the two films and observe the effects of changing the transmission coefficient t. We find that the electron interference is reduced as t is reduced but its energy dependence is unchanged, so that the evaluation of VF is unaffected. The phonon structure from the Cu is also decreased with t. The measured energy gap is proportional to the amplitude of the interference effect, indicating that both measure the pair amplitude at the free surface of the Cu. The phonon structure in Cu is proportional to the induced gap squared, independent of whether the gap is varied by a change in thickness or in transition coefficient. For Cu we find VF = 1.06 x 10 s cm/sec and the dimensionless electron-phonon coupling constant ~ = 0.11 + 0.03.

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“…s.0-s ~ -~rR s (23) where A~ u~k is the value deep in the S layer. This correction arises by the small depression of As at x = 0 which results from the ultra thin N layer.…”

Section: A Physical Basis For Proximity Electron Tunneling Spectroscomentioning

confidence: 99%

Proximity electron tunneling spectroscopy I. Experiments on Nb

et al. 1980

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A quantitative proximity electron tunneling spectroscopy (PETS) is demonstrated for the study of strong coupling superconductors which do not form suitable insulating oxides for conventional McMillan-Rowell tunneling spectroscopy. Proximity junctions of the form C-AI203-AI/ S are employed, with A1 thickness d~r <-100 A. Here S is the superconductor of interest and C is any convenient counterelectrode. The physical basis for the method, experimental techniques, and data obtained from foils of Nb are presented. The results for Nb include the energy-dependent pair potential As(E), the renormalization function Z(E), effective phonon spectrum a 2F(to), electron-phonon coupling constant A, and Coulomb pseudopotential lz *. A full discussion of the underlying theory and details of the methods of analysis employed to obtain, in addition, the pair potential of the Al proximity layer are contained in a following paper.

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Phonon structure in the tunneling characteristics of thin proximity effect sandwiches

Cited by 58 publications

References 31 publications

Transport properties of two‐dimensionally fused zinc porphyrins from linear‐response approach

Transport properties of two‐dimensionally fused zinc porphyrins from linear‐response approach

Tunneling investigation of Cu-Pb proximity sandwiches. Barrier transmission effects

Proximity electron tunneling spectroscopy I. Experiments on Nb

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