2015/08/31 by Yundi Quan, Warren E. Pickett · 1 citation
Physics and Astronomy · #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.93.104526
published as Phys. Rev. B 93, 104526 (2016) · 13 pages, 10 figures
arxiv created 2015/09/03 · arxiv updated 2016/03/30
The superconducting phase of hydrogen sulfide at Tc=200 K observed by Drozdov and collaborators at pressures around 200 GPa is simple bcc Im-3m H3S, predicted beforehand by Duan \it et al., has experimental confirmation. The various "extremes" that are involved -- pressure, implying extreme reduction of volume, extremely high H phonon energy scale around 1500K, extremely high temperature for a superconductor -- necessitates a close look at new issues raised by these characteristics in relation to high Tc. We use first principles methods to analyze the H3S electronic structure, particularly the van Hove singularities (vHs) and the effect of sulfur. Focusing on the two closely spaced vHs near the Fermi level that give rise to the impressively sharp peak in the density of states, the implications of strong coupling Migdal-Eliashberg theory are assessed. The electron spectral density smearing due to virtual phonon emission and absorption needs to be included explicitly to obtain accurate theoretical predictions and current understanding. Means for increasing Tc in H3S-like materials are addressed.