Superconducting Hydrides Under Pressure

The measurement of superconductivity at above 200 K in compressed samples of hydrogen sulfide and in lanthanum hydride at 250 K is reinvigorating the search for conventional high temperature superconductors. At the same time, it exposes a fascinating interplay between theory, computation, and experiment. Conventional superconductivity is well understood, and theoretical tools are available for accurate predictions of the superconducting critical temperature. These predictions depend on knowing the microscopic structure of the material under consideration, which can now be provided by computational first-principles structure predictions. The experiments at the megabar pressures required are extremely challenging, but, for some groups at least, permit the experimental exploration of materials space. We discuss the prospects for the search for new superconductors, ideally at lower pressures.