Orbital selective hole- and hole-pair formation and Bose condensation in high-temperature superconductors

Miguel Alario-Franco is recognised not only for his seminal experimental advances in the field of High Tc superconductivity but also for his incisive observations on the advances and challenges in that field. In 1995, he highlighted the need for “a new theme” to unite the chemistry and the physics of this spectacular natural phenomenon following the advance by Bednorz and Muller, that surely ranking as one of the greatest-ever discoveries in science. We review the remarkable recent advances that showed hole-pairing in the cuprates is found at temperatures above Tc; first proposed over three decades ago by Mott and Alexandrov. We highlight that the pairing itself will be ‘orbital-selective’ where holes of predominantly one specific orbital character bind to form the Cooper pairs which then condense to yield the High Tc state at a critical density and temperature. Here, a collection of friends and colleagues of Miguel from the disciplines of chemistry, physics and electronic engineering outline this as a working, chemically-intuitive model in the search for other High Tc materials.