The classic theory of superconductivity, developed by John Bardeen and colleagues, doesn't explain why such excellent conductors as gold and copper never transition to a superconducting state. New research gives a simple answer: it all comes down to the stiffness of the electron 'sheet' that electrons travel across. If this sheet is taut, electrons trip over bumps and lose energy: that’s resistance. For superconductivity to happen, the sheet must be soft, like a film on water, able to ripple. When stiffness drops to negative values, the sheet starts pushing electrons along, and they glide without friction.
The discovery sorts all metals into three groups: those with enhanced superconductivity (where the waves are short), those with ordinary superconductivity (infinitely long waves), and those where the sheet won’t bend at all: there, the chaotic motion of electrons keeps them from pairing up. Thus, for the first time, a simple rule predicts the behavior of any element in the periodic table.
Even at temperatures a few thousandths of a degree above absolute zero, gold remains an ordinary conductor, a record-setting stubbornness against superconductivity among pure metals.