Laser induced infrared spectral shift of the MgB2:Cr superconductor films

• It was established that FTIR spectra may be powerful tool for studies of photoinduced MgB2:Cr superconductors.
• The sign of the spectral shift is different depending on the laser wavelengths.
• The DFT calculations and temporary photovoltaic response confirm the dominant role of anharmonic phonons.

During illumination of the MgB2:Cr2O3 films it was established substantial spectral shift of the infrared spectra in the vicinity of 20–50 cm−1. The excitations were performed by nanosecond Er:glass laser operating at 1.54 μm and by microsecond 10.6 μm CO2 laser. The spectral shifts of the IR maxima were in opposite spectral directions for the two types of lasers. This one observed difference correlates well with spectral shift of their critical temperatures. The possible explanation is given by performance of DFT calculations of the charge density redistribution and the time kinetics of the photovoltaic response. To understand the kinetics of the photoinduced processes the time kinetics of photoresponse was done for the particular laser wavelengths.

Changes of infrared spectra for the MgB2:Cr samples at different external laser power densities of CO2 laser.Figure optionsDownload as PowerPoint slide