Agenda

Prochain séminaire LANEF/Matériaux Quantiques :

Jeudi 5 octobre 2023 à 14h00

Owen Moulding (Institut Néel)

“ Pressure induced formation of cubic lutetium hydrides ”

Pour accéder à ce séminaire :

Institut Néel CNRS, Bâtiment K, Salle Rémy Lemaire  (K223)

Résumé : It has been quite a year for superconductivity. After the condemnation of superconductivity in carbonaceous-sulfur hydride and the subsequent retraction of the corresponding paper, the fervent quest for room-temperature superconductivity continued once more and rather quickly bore fruit. Twice within five months in fact, but in this talk I will only discuss nitrogen-doped lutetium hydride and Dias’ second foray into discovering another room-temperature superconductor. As claimed in the Dasenbrock-Gammon paper [1], this purported new superconductor has a critical temperature of 294K at a pressure of 1GPa, whilst the subsequent patent [2] on the wonder material claimed superconductivity at ambient pressure. After heated discussions, tireless work, and in spite of the reported discrepancies, the impressive efforts made by the high-pressure community have resulted in another potential retraction. In this seminar, I shall discuss our Raman spectroscopy and X-ray diffraction results on our own synthesised lutetium hydrides [4]. Upon applying 2GPa, we observe a structural transformation and decomposition of our pure trigonal lutetium trihydride to a biphasic mixture of cubic compounds that structurally appear similar to both the samples of Dasenbrock-Gammon et al. [1] and Xing et al. [3]. Despite the similarities, we come to different conclusions on the compounds and structures present due to contradictions present in the previous structural analyses. We also conclude from EDX measurements that our sample does not contain any nitrogen-based compounds in contrast to the others. In the light of this, I will discuss the synthesis methods used and the likelihood of forming nitride compounds. Overall, we come to the conclusion that a mixture of Fm-3m LuH2+x and a novel Ia-3 compound are present. Together, these phases resolve the structural contradictions while no longer requiring the formation of N-doped lutetium hydride.

[1] N. Dasenbrock-Gammon et al. Nature 615, 244 (2023)
[2] R.L. Dias, High temperature and low pressure superconductor, PCT/US2022/038408 (2023)
[3] X. Xing et al. Arχiv: 2303.17587[cond-mat] (2023)
[4] O. Moulding et al. Arχiv: 2304.04310v2[cond-mat] (2023), submitted to PRB

Les organisatrices :

Elsa Lhotel (elsa.lhotel@neel.cnrs.fr)
Florence Levy-Bertrand (florence.levy-bertrand@neel.cnrs.fr)