Strong Electron-Hole Symmetry Breaking in the High Temperature Superconductor H₃S.

A favorable combination of strong electron-phonon coupling (EPC), high phonon frequency and substantial density of states (DOS) near the Fermi energy was predicted¹ to produce a record superconducting critical temperature T_c around 200K at high pressure, quickly followed by the experimental discovery by Drozdov et al.² up to 203K at 160 GPa pressure. Several theoretical papers have confirmed and elaborated on the new phenomena that arise in H₃S. Here we employ first principles methods that reveal new aspects of H₃S. The electron and phonon self energies are calculated using the EPW code, and we analyze effects of the two nearby van Hove singularities (vHs) that create a sharp and narrow peak of the electron DOS in this material. Several features emerge: The interacting DOS (the spectral density) is severely affected by the strong electron-phonon coupling, and the electronic spectrum displays extreme examples of band renormalization and broadening that have been suggested to arise from strong EPC. Phonon self-energy features will also be presented.

[1] D. Duan et al., Sci. Rep. 4, 6968 (2014).
[2] A.P. Drozdov et al., Nature (London) 525, 73 (2015).