Calculated sound velocity and elastic moduli changes of FeTe0.5Se0.5 at the superconducting transition

Abstract

The room temperature sound velocity in FeTe0.5Se0.5 superconductor has been measured using the pulsed-echo overlap ultrasonic technique. The samples were prepared using the solid-state reaction method at ambient pressure. Using these ultrasonic measurements we performed calculations that showed a step discontinuity in the bulk modulus, ∆BB=4ppm, Young's modulus, ∆YY=8ppm and longitudinal sound velocity, ∆vLvL=2ppm at Tc. The calculated acoustic Debye temperature, θD=334K indicated that FeTe0.5Se0.5 is slightly softer than the copper oxide based superconductor and hence the lower Tc. The calculated electron-phonon coupling in the two-dimensional van Hove scenario is, λvH=0.024.