Experimental Detection of Sign-Reversal Pairing in Iron-Based Superconductors

We propose a modified Josephson corner-junction experiment which can test whether the order parameter in the iron pnictides changes sign between the electron and hole pockets of the Fermi surface.Comment: 2 pages, 2 figures; After this paper was completed, we found a similar idea had been proposed by arXiv: 0812.4416: Published versio

The Elusive Bose Metal

The conventional theory of metals is in crisis. In the last 15 years, there has been an unexpected sprouting of metallic states in low dimensional systems directly contradicting conventional wisdom. For example, bosons are thought to exist in one of two ground states: condensed in a superconductor or localized in an insulator. However, several experiments on thin metal alloy films have observed that a metallic phase disrupts the direct transition between the superconductor and the insulator. We analyze the experiments on the insulator-superconductor transition and argue that the intervening metallic phase is bosonic. All relevant theoretical proposals for the Bose metal are discussed, particularly the recent idea that the metallic phase is glassy. The implications for the putative vortex glass state in the copper-oxide superconductors are examined.Comment: Double-spaced with five .eps files at end of tex