• Open Access

Pressure-Induced Hydrogen-Hydrogen Interaction in Metallic FeH Revealed by NMR

Thomas Meier, Florian Trybel, Saiana Khandarkhaeva, Gerd Steinle-Neumann, Stella Chariton, Timofey Fedotenko, Sylvain Petitgirard, Michael Hanfland, Konstantin Glazyrin, Natalia Dubrovinskaia, and Leonid Dubrovinsky
Phys. Rev. X 9, 031008 – Published 17 July 2019
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Abstract

Knowledge of the behavior of hydrogen in metal hydrides is the key for understanding their electronic properties. Here, we present an H1NMR study of cubic FeH up to 202 GPa. We observe a distinct deviation from the ideal metallic behavior between 64 and 110 GPa that suggests pressure-induced H-H interactions. Accompanying ab initio calculations support this result, as they reveal the formation of an intercalating sublattice of electron density, which enhances the hydrogen contribution to the electronic density of states at the Fermi level. This study shows that pressure-induced H-H interactions can occur in metal hydrides at much lower compression and larger H-H distances than previously thought and stimulates an alternative pathway in the search for novel high-temperature superconductors.

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  • Received 4 March 2019
  • Revised 13 May 2019

DOI:https://doi.org/10.1103/PhysRevX.9.031008

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

  1. Research Areas
  1. Physical Systems
Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Thomas Meier1,*, Florian Trybel1, Saiana Khandarkhaeva1, Gerd Steinle-Neumann1, Stella Chariton1, Timofey Fedotenko2, Sylvain Petitgirard3, Michael Hanfland4, Konstantin Glazyrin5, Natalia Dubrovinskaia2, and Leonid Dubrovinsky1

  • 1Bayerisches Geoinstitut, University of Bayreuth, D-95447 Bayreuth, Germany
  • 2Material Physics and Technology at Extreme Conditions, Laboratory of Crystallography, University of Bayreuth, D-95447 Bayreuth, Germany
  • 3Institute of Geochemistry and Petrology, Department of Earth Sciences, Eidgenössische Technische Hochschule Zürich, S-8092, Switzerland
  • 4European Synchrotron Radiation Facility (ESRF), F-38043 Grenoble Cedex, France
  • 5Deutsches Elektronen-Synchrotron (DESY), D-22603, Hamburg, Germany

  • *thomas.meier@uni-bayreuth.de

Popular Summary

The key to room-temperature superconductivity may come from metal hydrides, compounds in which a metal is bonded to hydrogen. Recent experiments have shown that these materials become superconductive at temperatures of 260 K and pressures of hundreds of gigapascals in diamond anvil cells. Further progress requires a deeper understanding of the electronic properties of hydrogen atoms, which is limited to theoretical predictions because of the lack of spectroscopic probes that can be used in these extreme conditions. Here, we use a novel high-pressure nuclear magnetic resonance method to investigate the electronic properties of hydrogen atoms in iron hydride.

We load samples of iron hydride into diamond anvil cells and ratchet the pressure up to 202 GPa. We then probe the electronic properties of the sample using nuclear magnetic resonance, which induces nuclear spin transitions via radio-frequency irradiation under an external magnetic field. We find that the application of pressure leads to the formation of a sublattice of free-electron gas connecting all hydrogen atoms, raising their ability to contribute to the electronic density of states, which is a prerequisite for high-temperature superconductivity. These interactions are found at distances between hydrogen atoms that are significantly longer than expected from theoretical predictions and might lead to a novel approach for the search of new high-temperature superconductors.

This research lays the foundation for the investigation of exotic hydrogen-rich superhydrides, which are believed to hold the key to room-temperature superconductivity.

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Vol. 9, Iss. 3 — July - September 2019

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