Crystal structure of the superconducting phase of sulfur hydride

Abstract

A superconducting critical temperature above 200 K has recently been discovered in H2S (or D2S) under high hydrostatic pressure1, 2. These measurements were interpreted in terms of a decomposition of these materials into elemental sulfur and a hydrogen-rich hydride that is responsible for the superconductivity, although direct experimental evidence for this mechanism has so far been lacking. Here we report the crystal structure of the superconducting phase of hydrogen sulfide (and deuterium sulfide) in the normal and superconducting states obtained by means of synchrotron X-ray diffraction measurements, combined with electrical resistance measurements at both room and low temperatures. We find that the superconducting phase is mostly in good agreement with theoretically predicted body-centered cubic (bcc) structure for H3S (Ref.3). The presence of elemental sulfur is also manifest in the X-ray diffraction patterns, thus proving the decomposition mechanism of H2S to H3S + S under pressure4–6.

Emergent Magnéli-type crystal phases and their mixture in pressurized sulfur hydride

“…Although possibilities of unconventional mechanisms are still under investigation [6,21,[23][24][25], these first-principles results strongly suggest that the phonon-mediated pairing has a pivotal role, which is also in accord with the experimentally observed hydrogen isotope effect [1]. According to the recent X-ray diffraction measurement [2], the observed record Tc is not of the solid phases of H 2 S, but of its decomposition product H 3 S. In prior to the first experimental discovery, P1 and Cmca phases of H 2 S and R3m and Im3m phases of H 3 S have been predicted to be stable and metallic at pressures above 100 GPa [3,4]. In particular, the electron-phonon coupling in the latter phases has been estimated to be strong enough to reproduce the experimentally observed Tc over 200 K [3,4].…”

“…The recent discovery of high-temperature superconductivity in compressed H 2 S [1,2] has tremendous impact on the basic science. Its maximum transition temperature (Tc) is as high as 203K, which is higher than the long-standing champion data observed in Hg-cuprate.…”

“…However, the reaction and kinetic route(s) of the phase transformation to the high-Tc H 3 S phase has been elusive: The efficient experimental protocol to realize the highTc phases is still to be established as significant dependence on the experimental compression and annealing procedures has been reported [1,2,[30][31][32]. Phases with various structures and compositions have been proposed with the first-principles structure-search methods, some of which have been suggested as the intermediate products [8,16,30,31,33].…”

Superconductivity in Hydrides Doped with Main Group Elements Under Pressure

“…Theoretical studies, which have shown that the superconductivity observed in Ref. [38] arises primarily from an H 3 S phase [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] whose structure has been recently confirmed experimentally [56], will not be described within this short review. We will, however, discuss the results of first principles calculations carried out for the hydrides of phosphorus [57][58][59].…”

Perspective: Role of structure prediction in materials discovery and design

“…Searches over a much smaller number of stoichiometries were performed by Duan et al 29 Errea et al 17 also showed that anharmonic vibrations significantly reduce the T c of H 3 S-Im3m. The high-pressure cubic structure of H 3 S of space group Im3m in which the sulfur atoms lie on a body-centered cubic (bcc) lattice has now been confirmed by X-ray diffraction experiments, 30 see Fig. 1.…”