Temperature dependence of energy gap in Bi2Sr2CaCu2O8 by high resolution electron energy loss spectroscopy

High Resolution Electron Energy Loss Spectroscopy (HREELS) has been used to determine the magnitude and temperature dependence of the energy gap for Bi2Sr2CaCu2O8 single crystals cleaved in vacuum. The loss spectra are proportional to the frequency‐dependent resistivity ρ(ω), and thus the energy gap can be determined directly from the onset of ρ(ω), we find that at low temperature 2Δ=6.3kTc and that Δ(T) develops sharply for T<Tc. The similarity of these results to the predictions of models that consider pair‐breaking interactions suggests that higher Tc’s may be obtained in this material.