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, SimoneInvestigation
;Profeta, GianniPenultimo
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.File | Dimensione | Formato | |
---|---|---|---|
Sanna_Possible-explanation_2023.pdf
accesso aperto
Note: Articolo su rivista
Tipologia:
Documento in Post-print (versione successiva alla peer review e accettata per la pubblicazione)
Licenza:
Creative commons
Dimensione
512.5 kB
Formato
Adobe PDF
|
512.5 kB | Adobe PDF |
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.