  The use of high pressure to realize superconductivity in the vicinity of room
temperature has a long history, much of it focused on achieving this in
hydrogen rich materials. This paper provides a brief overview of the work
presented at this May 2018 conference, together with background on motivation
and techniques, the theoretical predictions of superconductivity in lanthanum
hydride, and the subsequent experimental confirmation. Theoretical calculations
using density functional based structure search methods combined with BCS type
models predicted a new class of dense, hydrogen rich materials superhydrides
with superconducting critical temperatures in the vicinity of room temperature
at and above 200 GPa pressures. The existence of a series of these phases in
the La H system was subsequently confirmed experimentally, and techniques were
developed for their syntheses and characterization, including measurements of
structural and transport properties, at megabar pressures. Four probe
electrical transport measurements of a cubic phase identified as LaH10 display
signatures of superconductivity at temperatures above 260 K near 200 GPa. The
results are supported by pseudo four probe conductivity measurements, critical
current determinations, low-temperature xray diffraction, and magnetic
susceptibility measurements. The measured high Tc is in excellent agreement
with the original calculations. The experiments also reveal additional
superconducting phases with Tc between 150 K and above 260 K. This effort
highlights the novel physics in hydrogen-rich materials at high densities, the
success of materials by design in the discovery and creation of new materials,
and the possibility of new classes of superconductors Tc at and above room
temperature.
