A pseudo-potential approach to superconducting state parameters of certain metals

Sharma, R.; Sharma, K. S.

doi:10.1007/bf01959496

Cited by 14 publications

(6 citation statements)

References 16 publications

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“…Pseudopotential formalism, which has successfully explained various properties of metals [6][7][8][9] and binary metallic glasses [10][11][12][13], has been extended in this work for ternary metallic glasses to study their superconducting behaviour.…”

Section: Theorymentioning

confidence: 99%

A pseudopotential approach to the superconducting state parameters of (Ni33Zr67)1−x M x (M=Ti, V, Co, Cu) ternary metallic glasses

Sharma¹,

Khan²,

Sharma

2005

Czech J Phys

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Superconductivity in ternary metallic glasses has been investigated using the model pseudopotential approach, which has been found quite successful in explaining superconductivity in metals, binary alloys and binary glasses. It is observed that this simple methodology successfully explains superconducting behaviour of ternary glasses without requiring the solution of Dirac equation for a many body problem or estimation of various interactions as required in ab-initio pseudopotential theory. In the present work superconducting state parameters of fourteen metallic glasses of (Ni-Zr)-M system (M----Ti, V, Co, Cu) have been determined in the BCS-Eliashberg-McMillan framework. It is observed that addition of V, Co, and Cu as the third element (M) to a binary metallic glass (Ni3a Zr67) causes the parameters A, To, a, and NoV to decrease, and Coulomb pseudopotential (#*) to increase with concentration of M, showing that the presence of third element (M) causes suppression of superconducting behaviour of the alloy. The decrease in Tr with increasing concentration of third element (M) may be attributed to the modifications in density of states at the Fermi level N(EF), and probable changes in the band structure of the alloy due to addition of the third element (M). Slight difference is noticed when Ti is added to the Ni33 Zr67 alloy. In this case Tc rises initially and then decreases with concentration of M, showing a peak at about x = 0.05. This indicates that on addition of Ti, 3d states grow near the Fermi level and hence contribute substantially to N(EF), favouring superconducting behaviour in this case. The present results for Tc show an excellent agreement with the experimental data. Quadratic Tc equations have been proposed, which provide successfully the Tr values of ternary metallic glasses under consideration.

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Section: Theorymentioning

confidence: 99%

A pseudopotential approach to the superconducting state parameters of (Ni33Zr67)1−x M x (M=Ti, V, Co, Cu) ternary metallic glasses

Sharma¹,

Khan²,

Sharma

2005

Czech J Phys

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“…where α 2 (ω)F (ω) is the spectral function which, when appropriately evaluated in the plane wave approximation for the scattering on the Fermi surface, yields [22]…”

Section: Theorymentioning

confidence: 99%

“…In the present work we employ Ashcroft's (Ash) potential [19] and the linear (lin) potential due to Sharma and Kachhava [20] along with six different forms of dielectric screening. These potentials have been successfuly used in the past for predicting superconducting state properties of metals [21][22][23][24] and binary alloys [25,26].…”

Section: Introductionmentioning

confidence: 99%

A pseudopotential approach to the superconducting state properties of metallic glass

Sharma¹,

Sharma²

1997

Supercond. Sci. Technol.

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The superconducting state properties of the metallic glass Ca 70 Mg 30 have been investigated in the BCS-Eliashberg-McMillan framework by extending this theory to the binary metal glasses. Pseudo ions with average properties have been considered to replace both types of ions in the system. Values of the superconducting state parameters, namely electron-phonon coupling strength (λ), Coloumb pseudopotential (µ * ), transition temperature (T c ), isotope effect exponent (α) and interaction strength (N 0 V ) have been worked out using Ashcroft's potential and the linear potential due to Sharma and Kachhava along with six different forms of dielectric screening. The form factors directly obtained from the screened pseudopotential of Veljkovic and Slavic have also been used to explicitly observe the effect of the dielectric screening on T c , α and N 0 V through µ * . The results obtained established the presence of a superconducting phase in Ca 70 Mg 30 glass.

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“…ω L and ω T for the component metals are taken from Sharma et al [31] and then the values of 〈ω 2 〉 for the MGs have been obtained by using Vegard's rule. θ D for the component metals is taken from [27] and its value for the MGs have been computed by using Grimwall's formula.…”

Section: Resultsmentioning

confidence: 99%

Effect of local field correction in screening dependence of superconducting state parameters for Be₉₀Al₁₀ and Be₇₀Al₃₀ metallic glasses

Sharma¹,

Gupta²,

Khan³

2005

Physica Status Solidi (b)

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The superconducting state parameters (SSP) viz. electron-phonon coupling strength (λ), Coulomb pseudopotential (µ *), transition temperature (T c ), isotope effect exponent (α) and interaction strength (N 0 V) for two metallic glasses, i.e. Be 90 Al 10 and Be 70 Al 30 , have been investigated by extending the BCSEliasberg-McMillan formalism for the metallic glass superconductors incorporating the effect of local field correction in dielectric screening functions which in turn become prominent in determining superconducting state parameters of the metallic glasses under consideration. We have employed eleven forms of dielectric screening functions -viz. Hartree, RPA, Modified Hubbard, Overhauser, Geldart -Vosko, Animalu, King -Cutler, SCS, Vashistha -Singwi, Ichimaru -Utsumi, and Farid et al. -in conjunction with Ashcroft's potential to predict superconducting state parameters. It is observed that the values of SSP are quite sensitive to the form of dielectric screening functions. In conclusion the present computed values of SSP for the RPA form of dielectric screening are in good agreement with the experimental values and other theoretical results for both glassy materials, which confirms the validity of the proposed formalism.

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A pseudo-potential approach to superconducting state parameters of certain metals

Cited by 14 publications

References 16 publications

A pseudopotential approach to the superconducting state parameters of (Ni33Zr67)1−x M x (M=Ti, V, Co, Cu) ternary metallic glasses

A pseudopotential approach to the superconducting state parameters of (Ni33Zr67)1−x M x (M=Ti, V, Co, Cu) ternary metallic glasses

A pseudopotential approach to the superconducting state properties of metallic glass

Effect of local field correction in screening dependence of superconducting state parameters for Be₉₀Al₁₀ and Be₇₀Al₃₀ metallic glasses

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A pseudo-potential approach to superconducting state parameters of certain metals

Cited by 14 publications

References 16 publications

A pseudopotential approach to the superconducting state parameters of (Ni33Zr67)1−x M x (M=Ti, V, Co, Cu) ternary metallic glasses

A pseudopotential approach to the superconducting state parameters of (Ni33Zr67)1−x M x (M=Ti, V, Co, Cu) ternary metallic glasses

A pseudopotential approach to the superconducting state properties of metallic glass

Effect of local field correction in screening dependence of superconducting state parameters for Be90Al10 and Be70Al30 metallic glasses

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Effect of local field correction in screening dependence of superconducting state parameters for Be₉₀Al₁₀ and Be₇₀Al₃₀ metallic glasses