Motivated by unexpected reports of a 26 K superconducting transition in elemental titanium at high pressure, we carry out an accurate ab initio study of its properties to understand the rationale for this observation. The critical superconducting temperatures (𝑇𝑐's) predicted under the assumption of a phononic pairing mechanism are found to be significantly lower than those experimentally observed. We argue that this disagreement cannot be explained by an unconventional coupling, as previously suggested, or by the existence of competing metastable structural phases. As a physically meaningful hypothesis to reconcile experimental and theoretical results, we assume the presence of Ti vacancies in the lattice. Our first-principles calculations indeed show that lattice vacancies can cause pressure-dependent phonon softening and substantially increase the electron-phonon coupling at high pressure, yielding computed 𝑇𝑐's in agreement with the experimental measurements over the full pressure range 150-300 GPa. We expect the proposed 𝑇𝑐 enhancement mechanism to occur on a general basis in simple high-symmetry metals for various types of defects.

Possible explanation for the high superconducting Tc in bcc Ti at high pressure / Sanna, Antonio; Pellegrini, Camilla; di Cataldo, Simone; Profeta, Gianni; Boeri, Lilia. - In: PHYSICAL REVIEW. B. - ISSN 2469-9950. - 108:21(2023), pp. 1-7. [10.1103/physrevb.108.214523]

Possible explanation for the high superconducting Tc in bcc Ti at high pressure

Sanna, Antonio
Primo
Investigation
;
di Cataldo, Simone
Investigation
;
Profeta, Gianni
Penultimo
Supervision
;
Boeri, Lilia
Ultimo
Supervision
2023

Abstract

Motivated by unexpected reports of a 26 K superconducting transition in elemental titanium at high pressure, we carry out an accurate ab initio study of its properties to understand the rationale for this observation. The critical superconducting temperatures (𝑇𝑐's) predicted under the assumption of a phononic pairing mechanism are found to be significantly lower than those experimentally observed. We argue that this disagreement cannot be explained by an unconventional coupling, as previously suggested, or by the existence of competing metastable structural phases. As a physically meaningful hypothesis to reconcile experimental and theoretical results, we assume the presence of Ti vacancies in the lattice. Our first-principles calculations indeed show that lattice vacancies can cause pressure-dependent phonon softening and substantially increase the electron-phonon coupling at high pressure, yielding computed 𝑇𝑐's in agreement with the experimental measurements over the full pressure range 150-300 GPa. We expect the proposed 𝑇𝑐 enhancement mechanism to occur on a general basis in simple high-symmetry metals for various types of defects.
2023
superconductivity; condensed matter physics; computational materials science
01 Pubblicazione su rivista::01a Articolo in rivista
Possible explanation for the high superconducting Tc in bcc Ti at high pressure / Sanna, Antonio; Pellegrini, Camilla; di Cataldo, Simone; Profeta, Gianni; Boeri, Lilia. - In: PHYSICAL REVIEW. B. - ISSN 2469-9950. - 108:21(2023), pp. 1-7. [10.1103/physrevb.108.214523]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1712207
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