Local electronic structure rearrangements and strong anharmonicity in YH3 under pressures up to 180\u2009GPa

J Purans,K V Klementiev,A D Rosa,V S Minkov,A A Ivanov,O Mathon,A P Menushenkov,S Pascarelli,S P Besedin,A Kuzmin,T Irifune,M I Eremets,I Pudza

doi:10.1038/s41467-021-21991-x

Abstract

The discovery of superconductivity above 250 K at high pressure in LaH10 and the prediction of overcoming the room temperature threshold for superconductivity in YH10 urge for a better understanding of hydrogen interaction mechanisms with the heavy atom sublattice in metal hydrides under high pressure at the atomic scale. Here we use locally sensitive X-ray absorption fine structure spectroscopy (XAFS) to get insight into the nature of phase transitions and the rearrangements of local electronic and crystal structure in archetypal metal hydride YH3 under pressure up to 180 GPa. The combination of the experimental methods allowed us to implement a multiscale length study of YH3: XAFS (short-range), Raman scattering (medium-range) and XRD (long-range). XANES data evidence a strong effect of hydrogen on the density of 4d yttrium states that increases with pressure and EXAFS data evidence a strong anharmonicity, manifested as yttrium atom vibrations in a double-well potential.

Highlights

The discovery of superconductivity above 250 K at high pressure in LaH10 and the prediction of overcoming the room temperature threshold for superconductivity in YH10 urge for a better understanding of hydrogen interaction mechanisms with the heavy atom sublattice in metal hydrides under high pressure at the atomic scale
C a pffiffiffi Fig. 2 The crystal structure of YH3. a Pressure dependence of the interatomic distance Rð Yð0Þ À Yð1Þ Þ 1⁄4 a= 2, for fcc YH3 obtained from X-ray diffraction (XRD) versus Y K-edge EXAFS data; b Crystal structure of fcc YH3 phase
Y(0) and Y(2) denote yttrium atoms in the corners of the cube, while Y(1) atoms are in the centers of nearest faces and Y(3) atoms are in the centers of the neighbor faces

Summary

Introduction

The discovery of superconductivity above 250 K at high pressure in LaH10 and the prediction of overcoming the room temperature threshold for superconductivity in YH10 urge for a better understanding of hydrogen interaction mechanisms with the heavy atom sublattice in metal hydrides under high pressure at the atomic scale. Some 150-200 GPa are required, which can be attained by the diamond anvil cell (DAC) technique These findings, together with advances in development of computational methods (see Flores-Livas[10] for the review), prove the concept that high Tc can be attained in systems containing light elements (which promote high frequency of the lattice vibrations)—hydrogen being an extreme case[11]. It is unclear how hydrogen under high pressure interacts with the sublattice of heavy atoms in metal hydrides at the atomic scale.

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