Dw. Zhou, Quantum tunneling cyclic loop in high temperature superconductor probably is the microscopic origin of high temperature superconductivity, PHYSICA C, 341, 2000, pp. 203-204
4-particle (electrons or electrons with hole) or higher order quantum tunne
ling cyclic loops (QTCLs) in real space may play a key role in high Tc supe
rconductivity. Because of the existence of mixed valences on the CuO2 plane
, the electron/holes in high Tc superconductor are weekly localized and str
ongly correlated thus able to form QTCL. The QTCLs have k=0 in the center o
f 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. As a resu
lt of the strong correlation between those tunneling loops, high Tc superco
nductivity will occur if the connectivity of tunneling loops is large enoug
h to form an infinite cluster, under these conditions: T<Tc and H<Hc. This
high Tc superconducting transition is strong angular momentum related, is a
special kind of percolation transition which is consistent with the experi
mental results of uniaxial stress experiments and of thermal expansion meas
urements. This model is consistent with the fact that the coherence length
of high temperature superconductor is in the order of 5-20 angstroms. QTCL
model is consistent with gauge invariance and the observation of doped carb
on 60 superconductors and superfluid He-3.