Dissipative-regime measurements as a tool for confirming and characterizing near-room-temperature superconductivity

The search for new superconducting materials approaching room-temperature benefits from having a variety of testing methodologies to confirm and characterize the presence of superconductivity. Often, the first signatures of new superconducting species occur incompletely and in very small volume fractions. These trace amounts may be too weak to produce an observable Meissner effect and the resistance may not go completely to zero if the percolation threshold is not met. Under these conditions, secondary behavior—such as transitions or cross overs in the temperature dependence of magnetoresistance, magnetic irreversibility, or thermopower—are often used as indications for the presence of superconductivity. Our group has developed a rather unique set of fast-timescale and dissipative transport measurements that can provide another tool set for confirming and characterizing suspected superconductivity. Here, we provide some background for these methods and elucidate their collaborative value in the search for new superconducting materials.