THE THEORETICAL STUDY OF DYNAMIC THERMAL EXPANSION OF Bi-BASED HIGH T_c SUPERCONDUCTORS
Bi系高Tc超导体动态热膨胀反常行为理论初探

The dynamic process of thermal expansion of Bi-based high-Tc superconductors is studied theoretically. For normal and superconducting states, two groups of parameters are obtained to fit the experimental data, the agreement is good. Compared with the normal state, the anharmonic effects are greatly enhanced in the superconducting state. Both of the asymmtry of the mutual repulsion of the atoms and phonon softening are enhanced in the superconducting state, especially, the increase of the softening of phonons is much more enormous, up to 103 magnitude. In the end, the mechanism of the high-Tc Superconductors is discussed preliminarily.