2.1 Introduction of YBCO Yttrium-Barium-Copper-Oxide (YBCO) is a type II high temperature superconductor (Rana et al., 2016) called 1-2-3 superconductors. The superconductivity is depending on the hole and electron concentration present. Previous research finds that YBCO has highest transition temperature (TC) that is 92 K. The unit cell of the YBCO is an orthorthombic structure. The CuO2 molecule are interconnected with CuO3 and then provide additional electron density. YBCO is a common element studied for synthesizing Superconductor. The YBCO in bulk form can lift a small magnet when immersed in nitrogen liquid. This is caused by the repulsion of the YBCO magnetic field. This phenomenon is called Meisner Effect. YBCO is a critical temperature and single grain superconductors…show more content… This allows the electron pairs move without any resistance. As a result, the two electrons are bound together to form Cooper pairs. Cooper pair bonding force called energy gap Eg is 10-3eV, which will cause low-temperature superconductors.
At transition temperature, the vibration of the virtual phonon is gone. The virtual phonon will produce positive charge between them. Electron which has negative charge will attracted, thus will produce two electron moved at the same time. The two electron pairs are called Cooper pairs. Part of Cooper pairs will split and cause excess electrons interact with the other Cooper pairs. This will cause the electron move in straight line without colliding with the lattice atom (Pair, 2016).
While superconductors are cooled to very low temperatures, electrons of a Cooper pair still formed. When superconductors absorb heat, vibrations in the lattice will grow and break Cooper pairs and eliminate the conductivity properties of the material. Figure 2.3 The establishment of cooper pairs in the lattice of positively charged