The arrival of high temperature superconductors*

The attainment of high temperature superconductivity has been considered a major advancement of modern science. It was the seminal discovery of the first cuprate high temperature superconductor, the Ba-doped La$_{2}$CuO$_{4}$, with a $T_{c}$ of 35 K in 1986 by Alex M\"{u}ller and George Bednorz of IBM Zurich Lab,\footnote{J. G. Bednorz and K. A. M\"{u}ller, Z. Phys. B 64, 189 (1986).} who were awarded the Nobel Prize in 1987, that ushered in the era of cuprate high temperature superconductivity. It was the first liquid nitrogen high temperature superconductor, YBa$_{2}$Cu$_{3}$O$_{7}$ with a $T_{c}$ of 93 K discovered in 1987 by Paul C. W. Chu, Maw-Kuen Wu and colleagues in the respective groups at the University of Houston and the University of Alabama at Huntsville\footnote{M. K. Wu et al., Phys. Rev. Lett. 58, 908 (1987).} that heralded the new era of high temperature superconductivity, drastically changing the psyche of superconductivity research and bringing superconductivity applications a giant step closer to reality. In the ensuing years, many high temperature superconductors have been found, leading to the current record $T_{c}$ of 134 K which was observed by A. Schilling et al.\footnote{A. Schilling et al., Nature 363, 56 (1993).} of ETH in 1993 in HgBa$_{2}$Ca$_{2}$Cu$_{3}$O$_{9-\delta}$ at ambient and later raised to 164 K under 30 GPa by L. Gao et al.\footnote{L. Gao et al., Phys. Rev. B 50, 4260(R) (1994).} In the present talk, I shall briefly recall a few events leading to and during the arrival of high temperature superconductivity. The prospects for future superconductors with higher $T_{c}$ will also be discussed.