The universality of pseudogap phenomenon in the normal state of high temperature cuprate superconductors

The pseudogap phenomenon in the normal state of Sn-, Mg- and Cd-doped Hg-12 23 ceramic superconductors was studied based on the results of resistivity versus temperature measurement. By using the data obtained in the resistivi ty measurement a logarithmic deviation of the conductivity versus inverse t emperature, i.e. ln[sigma (T) - sigma (N)(T)] versus 1/T was constructed to study the pseudogap which is opened at T* far above the critical temperatu re T-C of the superconductors. The magnitude of the pseudogap was measured through the slope of the linear part in these plots. It is surprising that the differentiation of these plots with respect to the inverse temperature shows a constant within very wide temperature range. Similar as in the ener gy gap measurement in the semiconductors, this constant should represent th e pseudogap of the normal state for the materials interested. The occurrenc e of the characteristic temperatures T*, Ts and TF can be interpreted by ou r microscopic theory. The physical significances of the variation in the ma gnitude of the pseudogap Delta (PG) with respect to temperature are related to the kinetic energy of the quasiparticles involved in the system. The pl ot of T* against the molar fraction of the Sn-doping a: is linear. However, the data of T* for the other doping elements Mg and Cd are scattered from the linear relationship for the Sn-doped (Hg1-x Sn-x)-1223 system. However, when we plot the relationship between T* against T-C the data of T* for di fferent doping elements fall on the same curve of bend fingerlike shape. Th is indicates that the intrinsic parameters T* and Te satisfy a universal re lationship. The ratio Delta (PG)/(k(B)T(F)) is expressible as a linear func tion of T-C when the critical temperature is below similar to 129 K; while for samples that have critical temperature greater than 129 K this ratio is expressible as a quadratic polynomial function of T-C. The universality re lationship is also hold for this ratio against T-C.