Superconductivity, the phenomenon of vanishing electrical resistivity, was first discovered by the Dutch physicist Heike Kamerlingh Onnes in 1911 when he was able to produce liquid helium and cool mercury down to below 4.2 K. At that time, it was not known how the conductivity of a metal would behave if the temperature was reduced close to the absolute zero. Onnes was stunned to see that the resistance in a mercury wire in liquid helium suddenly dropped below a measurable value. For this discovery, Onnes received the Nobel Prize in Physics in 1913.
Since the discovery that mercury becomes superconducting at 4.2 K, intense research has been devoted to find other superconductors. In fact, most elemental metals were found to be superconducting, but only if they are cooled down to very low temperatures. The ultimate goal is to find a material that can superconduct at room temperatures, but the search has been so far unsuccessful even one century after Onnes’ initial discovery. Surprisingly, there is no theoretical limit to the transition temperature in conventional superconductivity, and the most promising candidate material is metallic hydrogen, which has been predicted to superconduct at ambient temperatures.
To produce metallic hydrogen it is necessary to expose it to extremely high pressures beyond current experimental capabilities, and so far there have been no conclusive reports on its successful synthesis. However, recent high-pressure experiments have shown that a hydrogen rich compound, hydrogen sulfide, has a superconducting transition temperature of 203 K (“only” -70° C) at 200 GPa. This is the closest to a room-temperature superconductor that has ever been reported.
My research is aimed at using computational tools to explore both the chemical and structural space to search for new superconducting materials. In many cases, the superconducting properties strongly depend on the chemical and structural properties. Hence, I use simulations to identify rules that define if a metal will be a good superconductor or not prior to its synthesis.