Taking a step back and looking at the “superconducting dome” from a distance

Abstract

In my short essay in honor of Karl-Alex Müller, I would like to deal with some aspects that have been on my mind since the beginning of my own research. Some of the facts and questions mentioned here have been known or clarified for a long time, others not. For example, I think that the fact that superconductivity occurs almost spontaneously in many cuprates close to the optimum doping level has been insufficiently (or not at all) investigated. Much research has been done in the regions outside the optimal doping, be it underdoped or overdoped. I would like to deviate from the "mainstream" for a moment and ask whether these regions are really so relevant for the occurrence of superconductivity, or whether they simply serve to interfere with it - a thought which I am sure has been expressed by others and which would certainly lead (or had already led) to lively discussions with Karl-Alex Müller.