Multiband and impurity effects in infrared and optical spectra of MgB2

Kuzmenko, A. B.

doi:10.1016/j.physc.2007.02.008

Cited by 31 publications

(34 citation statements)

References 67 publications

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“…A theoretical study of ab initio electronic structure calculations on the compound, MgB2' using the Full Potential Linearized Augmented Plane Waves method within the Generalized Gradient Approximation, indicates the limitations of a theory describing the superconducting state in this material [6]. And the effect of pressure in the value of Tc [7]. Further study of the optical and far infrared measurements on MgB2 is given.…”

Section: Introductionmentioning

confidence: 99%

The investigations of electronic structure, optical and magnetic properties of MgB<inf>2</inf> nanosheets

Zaari

Naji

Hachimi

et al. 2014

2014 International Renewable and Sustainable Energy Conference (IRSEC)

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First principles calculations were performed to study the electronic structures of Magnesium diboride (MgBz) bulk and nanosheet with different layer and thickness in order to understand the influence of layer number and thickness on electronic and optical properties for this compound, using the Full Potential Linearized Augmented Plane Waves (FP-LAPW) method with the Generalized Gradient Approximation (GGA) implemented in Wien2k code. It is shown that the MgBz is superconductor with Tc=39K, however MgBz sheet become a nonmagnetic semiconductor and good transparent in the visible range,the absorption coefficient decrease and the superconductor properties appears again with increasing number of layers.

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Section: Introductionmentioning

confidence: 99%

The investigations of electronic structure, optical and magnetic properties of MgB<inf>2</inf> nanosheets

Zaari

Naji

Hachimi

et al. 2014

2014 International Renewable and Sustainable Energy Conference (IRSEC)

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“…The same can be done in multi-band case, while keeping in mind that the interband impurity scattering also enters implicitly through the gap function ∆ n (ω), equations (1)(2)(3)(4). To this end Z n (ω) in (4) is replaced by (7) and one has…”

Section: Theorymentioning

confidence: 99%

Effect of disorder on the far-infrared conductivity and on the microwave conductivity of two-band superconductors

Mitrović¹

2008

J. Phys.: Condens. Matter

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Abstract. We consider the far-infrared and the microwave conductivities of a two-band superconductor with non-magnetic impurities.The strong coupling expressions for the frequency and temperature dependent conductivity of a twoband superconductor are developed assuming isotropic bands and interactions. Our numerical results obtained using realistic interaction parameters for MgB 2 are compared with experiments on this compound. We find that the available experimental results for the far-infrared conductivity of MgB 2 are consistent with multi-band superconductivity in the presence of a sufficiently strong interband impurity scattering. On the other hand, our numerical results for the microwave conductivity in the superconducting state indicate that the experimental results obtained on samples with the highest transition temperature T c are consistent with a low interband impurity scattering rate but depend sensitively on the ratio of the total scattering rates in the two bands. For the π-band scattering rate γ π not greater than the σ-band scattering rate γ σ there is a single, broad, low-temperature (at about 0.5T c ) coherence peak in the microwave conductivity. For γ π /γ σ =4-7 a high-temperature (at about 0.9T c ) coherence peak is dominant, but there is also a low-temperature peak/shoulder resulting from the contribution of the π-band carriers to the microwave conductivity. For γ π /γ σ ≫1 only the high-temperature coherence peak should be observable.

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“…4,8 In the superconducting state, on the contrary, a two-gap description of the far-IR spectrum of MgB 2 , based on independent BCS responses of and bands, did fail in describing experimental data. In fact, the far-IR response of the ab plane of MgB 2 appears to be dominated by the -band carriers.…”

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confidence: 99%

“…4 In the normal state, this technique can, indeed, distinguish the different contributions of the two bands ͑ and ͒ to the frequency-dependent conductivity. [4][5][6][7] In particular, reflectance measurements on the ab plane can provide values of the two corresponding plasma frequencies ⍀ i and scattering rates ␥ i =1/ i ͑i = , ͒. In the superconducting state, several studies have been performed in the terahertz or far-IR range ͑here defined by photon energies below 16 meV, frequency Ͻ 130 cm −1 , or Ͻ 4 THz͒ since a mark of the superconducting gap ⌬ is expected in the reflectance or transmittance spectrum at ប ϳ 2⌬ ͑optical gap͒ for an isotropic s-wave BCS superconductor.…”

mentioning

confidence: 99%

“…However, in the far-IR response evaluated with this model, the main feature shows up at ប ϳ 2⌬ when realistic values of the parameters ⍀ i , ␥ i , and ⌬ i are employed. 4 This inconsistency raises an important problem: while the dc transport properties and the dc-field penetration depth 13 can be described under the two-band parallel conductivity assumption, the present body of experimental evidence suggests that this assumption can be questioned when applied at terahertz frequencies in the superconducting state.…”

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confidence: 99%

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Two-band parallel conductivity at terahertz frequencies in the superconducting state ofMgB2

Ortolani

Dore²,

Castro³

et al. 2008

Phys. Rev. B

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The optical response of the two-band superconductor MgB 2 has been studied in the 0.7-4 THz range on films with very low impurity level. The effect of the high-energy gap is observed in the ratio R S / R N between the normal and superconducting state reflectance, while in a neutron irradiated film with a slightly higher impurity level, mainly the effect of the gap is evident, as reported in previous experiments. At terahertz frequencies, the electrodynamics of MgB 2 can be well described by the two-band parallel conductivity model and is dominated by the bands when the impurity level is only slightly higher than that of an ultraclean sample.

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Multiband and impurity effects in infrared and optical spectra of MgB2

Cited by 31 publications

References 67 publications

The investigations of electronic structure, optical and magnetic properties of MgB<inf>2</inf> nanosheets

The investigations of electronic structure, optical and magnetic properties of MgB<inf>2</inf> nanosheets

Effect of disorder on the far-infrared conductivity and on the microwave conductivity of two-band superconductors

Two-band parallel conductivity at terahertz frequencies in the superconducting state ofMgB2

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