Effect of disorder on the far-infrared conductivity and on the microwave conductivity of two-band superconductors - Condensed Matter > SuperconductivityReport as inadecuate




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Abstract: We consider the far-infrared and the microwave conductivities of a two-bandsuperconductor with non-magnetic impurities. The strong coupling expressionsfor the frequency and temperature dependent conductivity of a two-bandsuperconductor are developed assuming isotropic bands and interactions. Ournumerical results obtained using realistic interaction parameters for MgB$ {2}$are compared with experiments on this compound. We find that the availableexperimental results for the far-infrared conductivity of MgB$ {2}$ areconsistent with multi-band superconductivity in the presence of a sufficientlystrong interband impurity scattering. On the other hand, our numerical resultsfor the microwave conductivity in the superconducting state indicate that theexperimental results obtained on samples with the highest transitiontemperature $T {c}$ are consistent with a low interband impurity scatteringrate but depend sensitively on the ratio of the total scattering rates in thetwo bands. For the $\pi$-band scattering rate $\gamma {\pi}$ not greater thanthe $\sigma$-band scattering rate $\gamma {\sigma}$ there is a single, broad,low-temperature at about 0.5$T {c}$ coherence peak in the microwaveconductivity. For $\gamma {\pi}-\gamma {\sigma}$=4-7 a high-temperature atabout 0.9$T {c}$ coherence peak is dominant, but there is also alow-temperature peak-shoulder resulting from the contribution of the $\pi$-bandcarriers to the microwave conductivity. For $\gamma {\pi}-\gamma {\sigma}\gg$1only the high-temperature coherence peak should be observable.



Author: Bozidar Mitrovic

Source: https://arxiv.org/







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