Quantum tunneling cyclic loop in high temperature superconductor probably is the microscopic origin of high temperature superconductivity

Abstract

4-particle (electrons or electrons with hole) or higher order quantum tunneling cyclic loops (QTCLs) may play a key role in high Tc superconductivity. Because of the existence of mixed valences on the CuO 2 plane, the electron/holes in high Tc superconductor are weekly localized and strongly correlated thus able to form QTCL. The QTCLs have k=0 in the center of the mass frame, and a non-zero angular momentum. Each QTCL has total spin S=0. Each QTCL can contain 2 or more Cooper pairs in real space. The QTCL may explain superfluid 3He phenomenon, in which angular momentum is not equal to zero case. As a result of the strong correlations between those tunneling loops, high Tc superconductivity will occur if the connectivity of tunneling loops is large enough to form an infinite cluster, under these conditions: T<Tc and H<Hc. This high Tc superconducting transition is a special kind of percolation transition which is consistent with the experimental results of uniaxial stress experiments and of thermal expansion measurements. This microscopic dynamics process on CuO2 planes is consistent with the experimental results of uniaxial stress experiments and of thermal expansion measurements and many other experiments. Because of the existence of QTCL, half intrinsic flux quanta h/4e and higher order fractional flux quanta such as h/20e and other fractional flux quanta should be observed in all kind of high temperature superconductors. Some recent observations have indicated the above predictions. This model is consistent with the fact that the coherence length of high temperature superconductor is in the order of 5–20 angstroms. Therefore, the consideration of the microscopic dynamics in real space (not only in k-space) is necessary for a reasonable model. From quantum mechanics view, the coherent position exchange in a QTCL only changes the phase of a wavefunction of a QTCL and the energy of a QTCL is conserved, this is consistent with gauge invariance. This microscopic scale energy conservation and the phase relation is the foundation of high temperature superconductivity. This microscopic scale energy conservation and the phase of fractional flux quanta will be observed in all different high temperature superconductors as well as in those doped carbon 60 superconductors in the near future.