We introduce the effective Lagrangian with spontaneously broken density in the Sethna-Sachdev-Nelson formula, and propose one explanation for the increase of the positron diffusion lengthL+ in the liquid metal phase with temperature. It is shown that the effective mass of the positron in the liquid metal phase will decrease due to the restoration of the spontaneously broken density around the positron, when temperature increases.
Authors:N. Oshima, E. Hamada, T. Suzuki, K. Kondo, I. Kanazawa, and Y. Ito
Pulsed slow positrons were produced using a time-varying moderator bias with an interval of 82 ns; 97% of the positrons were
compressed within 2 ns width at the target position. Both the positron annihilation lifetime and Doppler broadening of the
positron annihilation radiation (DBPR) of polytetrafluoroethylene (PTFE) were measured as a function of the incident energy
of slow positrons. It was shown that the lifetime and intensity of the long-lived component of positron annihilation are independent
of the positron incident energy above 1.2 keV. However, the width of the Doppler-broadened annihilation γ-ray increased in
the energy region below 1.2 keV.