Bipartite character of electronic structure in compressed H₃S and its relation to the high-Tc superconductivity

The sulfur superhydride H₃S has attracted enormous interest since the discovery of the 200K superconductivity in this material under extreme pressure. According to the previous studies, its Tc is boosted by the peaked structure in the density of states (DOS) and its presence is robust against substitution of sulfur atoms to phosphorus etc.. Its persistence has been thought to emerge through some complicated interplay of the sulfur 3s, 3p and hydrogen 1s orbitals but clear explanation on it has yet been established. We disentangle the “complicated interplay” to clarify how the DOS peak emerges. In particular, we find that a sublattice model with decorated simple cubic structure well represents the electronic structure in this system near a two-dimensional manifold in the Brillouin zone, which is due to small inter-sublattice coupling dependent on the crystal wavenumber. We discuss this point and its possible relation to the robust DOS peak.