Emergent superconductivity in TaO3 at high pressures

Abstract

Tantalum (Ta) is an interesting transition metal that exhibits superconductivity in its elemental states. Additionally, several Ta chalcogenides (S and Se) have also demonstrated superconducting properties. In this work, we propose the existence of five high-pressure metallic Ta–O compounds (e.g., TaO₃, TaO₂, TaO, Ta₂O, and Ta₃O), composed of polyhedra centered on Ta/O atoms. These compounds exhibit distinct characteristics compared to the well-known semiconducting Ta₂O₅. One particularly interesting finding is that TaO₃ shows an estimated superconducting transition temperature (T_c) of 3.87 K at 200 GPa. This superconductivity is primarily driven by the coupling between the low-frequency phonons derived from Ta and the O 2p and Ta 5d electrons. Remarkably, its dynamically stabilized pressure can be as low as 50 GPa, resulting in an enhanced electron–phonon coupling and a higher T_c of up to 9.02 K. When compared to the superconductivity of isomorphic TaX₃ (X = O, S, and Se) compounds, the highest T_c in TaO₃ is associated with the highest N_EF and phonon vibrational frequency. These characteristics arise from the strong electronegativity and small atomic mass of the O atom. Consequently, our findings offer valuable insights into the intrinsic physical mechanisms of high-pressure behaviors in Ta–O compounds.