Optical properties of c-axis oriented superconducting MgB2 films.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Magnesium diboride (MgB2) is a well-known superconductor with a critical temperature (Tc) of around 39 K.
• Understanding the electronic properties of MgB2 films is crucial for developing superconducting applications.

Purpose of the Study:

• To investigate the temperature-dependent optical conductivities and dc resistivity of c-axis oriented MgB2 films.
• To determine the electronic parameters of MgB2, such as Drude plasma frequency and electron-phonon coupling.
• To explore the superconducting mechanism in MgB2, specifically investigating multigap superconductivity.

Main Methods:

• Measurement of temperature-dependent optical conductivities and dc resistivity.
• Analysis of normal state optical conductivities using the Drude model.
• Fitting of normal state resistivity data with the Bloch-Grüneisen formula.
• Examination of optical conductivity spectra below the critical temperature (Tc).

Main Results:

• Normal state ab-plane optical conductivities are well-described by the Drude model with a temperature-independent Drude plasma frequency (ωp,D ≈ 1.68 eV).
• Normal state resistivity is fitted by the Bloch-Grüneisen formula, yielding an electron-phonon coupling constant (λtr ≈ 0.13).
• Optical conductivity spectra below Tc indicate that MgB2 exhibits multigap superconductivity.

Conclusions:

• The study provides key electronic parameters for MgB2 films, including plasma frequency and electron-phonon coupling.
• The findings strongly suggest that MgB2 is a multigap superconductor, consistent with theoretical predictions.
• This research contributes to a deeper understanding of the fundamental properties of MgB2, aiding future technological applications.