Hot Hydride Superconductivity above 550 K*

The search for room temperature (RT) superconductivity (SC) has accelerated dramatically, driven by theoretical predictions that first indicated alloying dense hydrogen with other elements could produce conventional phonon-mediated SC at very high temperatures and at accessible pressures, and then with the success of structure search methods that have identified specific candidates and pressure-temperature (P-T) conditions for synthesis. As a result, experimental studies of simple binary hydrides under pressure have yielded high critical SC transition temperatures (T_c), of 260K in LaH₁₀, close to RT, at pressures near 180GPa. We successfully synthesized a metallic La based superhydride from La metal and NH₃BH₃, and find an initial multi-step transition with a T_c of 294K for the highest onset, in line with previous work[1],[2]. Subsequent thermal excursions to higher temperatures promoted a chemical reaction a ternary or higher order system, confirmed by X-ray diffraction. Although the reaction does not appear to be complete, the onset temperature was pushed from 294K to 556K. The results provide evidence for hot superconductivity well above RT, in line with recent predictions for a higher order hydride under P[3].
[1] Somayazulu et al. PRL 122 (2019).
[2] Drozdov et al. Nat. 569, 528–531 (2019).
[3] Sun, Y.et al. PRL 123 (2019)