Electron–phonon coupling properties in MgB₂observed by Raman scattering

Abstract

The influence of sintering temperature on the critical transition temperature, T c , for MgB 2 superconductor was investigated systematically with the aid of room temperature Raman scattering measurements and Raman spectral fit analysis. The Raman spectra for all samples can be fitted with one phonon peak coming from the E 2g mode at the point of the Brillouin zone and two peaks coming from sampling of the phonon density of states (PDOS) due to disorder. The enhanced E 2g mode in the Raman spectra with increasing sintering temperature shows gradual strengthening of the electron-phonon coupling (EPC) in MgB 2 , which is the reason why the T c of samples increases with increasing sintering temperature. The strength of electron-E 2g coupling is estimated to be about 2.0 ± 0.5, which is larger than the average strength of the coupling of electrons with all the phonon modes, ∼1.23. The T c dependence on the profiles of the PDOS peaks is described using the variation of the peaks' frequencies and linewidths in different samples.

Enhancing the Superconducting Properties of Magnesium Diboride Without Doping

“…The peak at ~600 cm −1 , the only Raman active mode for MgB 2 , is associated with the E 2 g in‐plane vibration mode of boron atoms . The E 2 g vibration mode can be affected by chemical substitution, lattice distortion, or strain . The phonon spectrum can be modified by variation in the phonon frequency and/or the electron–phonon interaction.…”

The effect of reduced graphene oxide addition on the superconductivity of MgB2

“…Therefore, the electron-phonon coupling intensity and the crystal distortion will influence the Raman shift and the line width of the Raman scattering. 22,23 As revealed by Fig. 6, a slight shift of the E 2g band to the low frequency range can be observed in doped samples when compared with the undoped sample, which gives an evidence of induced tensile strain as a result of doping.…”

High Critical Current Density MgB2

“…The Raman spectra for the pure MgB 2 are shown in Figure 5(a) and (b) to compare the cooling effects on the matrix. Both the spectra have been fitted with three peaks: ω 1 , ω 2 , and ω 3 [114][115][116]. Based on the previous results, ω 2 is the reflection of the E 2g mode at the Г point of the Brillouin zone in the simple hexagonal MgB 2 structure (space group: P6/ mmm), while ω 1 and ω 3 come from the lattice distortion.…”