The possibility of a liquid superconductor

Abstract

All superconductors are solids in their superconducting state, this canonical electronic state of matter presently having only been observed well below the melting temperature of the solid. The discovery of high-temperature superconductivity in cuprates has widened significantly our horizons of the theoretical understanding of the physical phenomenon. A number of observations point to the possibility that superconductors with a high superconducting transition temperature may not be conventional Bardeen-Cooper-Schrieffer (BCS) superconductors, but rather derive from the Bose-Einstein condensation of real-space pairs. While BCS superconductors exist in the solid state (probably with the exception of metallic liquid hydrogen at ultrahigh pressures), we argue here that a superconducting charged Bose liquid may be found in a true liquid state of condensed matter at ambient pressure. An experimental scenario is outlined in fluid metal-ammonia solutions for stabilizing and observing a high-temperature superconducting liquid (ca. 230 K) or at least a vitreous superconductor in the corresponding quenched solutions (ca. 160 K).