At very low temps. ( absolute zero , ) This gap can become " gapless " . It takes the minutest amount of energy to reach a Quantum Phase transition ; without heat . Now that's very interesting , is it not ? I think so . About a year ago I bought this Issue of Scientific American ( special report , Oct./2018 ) ; The Unsolvable Problem . About a month ago I finally started to read the article . Phase transition ; material goes through sudden and dramatic property change. ( Ice to liquid ) . But at extremely low temps. Absolute zero ; an insulator can become a superconductor by changing the magnetic field around the material or by pressure ; as well a soild can become a superfluid .