High temperature superconductivity in sulfur and selenium hydrides at high pressure

Abstract

Abstract. Due to its low atomic mass, hydrogen is the most promising element to search for hightemperature phononic superconductors. However, metallic phases of hydrogen are only expected at extreme pressures (400 GPa or higher). (2015)], shows that metallization of hydrogen can be reached at significantly lower pressure by inserting it in the matrix of other elements. In this work we investigate the phase diagram and the superconducting properties of the H-S systems by means of minima hopping method for structure prediction and density functional theory for superconductors. We also show that Se-H has a similar phase diagram as its sulfur counterpart as well as high superconducting critical temperature. We predict H3Se to exceed 120 K superconductivity at 100 GPa. We show that both H3Se and H3S, due to the critical temperature and peculiar electronic structure, present rather unusual superconducting properties.Under high pressure conditions, insulating and semiconducting materials tend to become metallic, because, with increasing electronic density, the kinetic energy grows faster than the potential energy. As metallicity is a necessary condition for superconductivity, generally becomes more likely under pressure [1,2]. Wigner and Huntington [3], already in 1935 suggested the possibility of a metallic modification of hydrogen under very high pressures. Ashcroft and Richardson predicted [4,5] hydrogen to become metallic under pressure and also the possibility to be a high temperature superconductor. The high critical temperature (T C ) of hydrogen [6-8] is a consequence of its low atomic mass leading to high energy vibrational modes and in turn to a large phase space available for electronphonon scattering to induce superconductivity [9]. However, the estimated metallization pressure [10,11] is beyond the current experimental capabilities [12][13][14][15]. It was only recently that hydrogen-rich compounds (chemically pre-compressed) started to be explored as a way to decrease the tremendous metallization pressure of pure hydrogen [16]. The first system explored experimentally was silane (SiH 4 ) [17]. Soon after, many others materials have been explored experimentally [18][19][20][21] and theoretically [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40].

Structure and Composition of the 200 K‐Superconducting Phase of H2S at Ultrahigh Pressure: The Perovskite (SH−)(H3S+)

“…[6] DFT calculations confirmed the proposed m Im3 structure of H3S as the lowest energy one. [2,7,8,9,10,11] The m Im3 structure of H3S (a = 3.089 Å) consists of two interpenetrating SH3 perovskite sublattices ( Figure 1a)) with a HH contact distance of 1.5 Å, which is very short compared with the van der Waals radii sum of 2.4 Å but very long compared with the HH single-bond distance 0.74 Å in H2. The decomposition, 3 H2S  2 H3S + S, implies that the XRD intensities of H3S and sulfur with -Po structure should have a 2:1 ratio.…”

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].…”

Possible High-Temperature Superconductivity in Hygrogenated Fluorine

“…The ideas of Ashcroft have been recently confirmed by the experiments of Drozdov et al [6] and a series of theoretical papers [7][8][9][10][11][12][13][14] that confirm hydrogen-based hightemperature superconductivity is realized in the sulfur *Corresponding Author: D. A. Papaconstantopoulos: Department of Computational and Data Sciences, George Mason University, Fairfax, Virginia 22030, USA, E-mail: dpapacon@gmu.edu compound H 3 S under 200 GPa pressure. Reference [8] presents a comprehensive set of calculations for H 3 S using the GGM theory.…”