By definition, superconductors are conductors with zero resistance at low temperatures. Do superconductors exist ideally, i mean whether zero resistance is practically possible?
There are many examples of superconductors, they are more than theory and have been produced for years. The problem is that they are very low temperature. The holy grail of such science is a room-temperature (and higher) superconductor that would be superconductive without the need for extensive cooling facilities.