The Role of Phonons and Oxygen Vacancies in Non-Cubic SrVO₃

Combining neutron diffraction with pair distribution function analysis, we have uncovered hidden reduced symmetry in the correlated metallic d¹ perovskite, SrVO₃. Specifically, we show that both the local and global structures are better described using a GdFeO₃ distorted (orthorhombic) model as opposed to the ideal cubic ABO₃ perovskite type. Recent reports of imaginary phonon frequencies in the density functional theory (DFT)-calculated phonon dispersion for cubic SrVO₃ suggest a possible origin of this observed non-cubicity. Namely, the imaginary frequencies computed could indicate that the cubic crystal structure is unstable at T = 0 K. However, our DFT calculations provide compelling evidence that point defects in the form of oxygen vacancies, and not an observable symmetry breaking associated with calculated imaginary frequencies, primarily result in the observed non-cubicity of SrVO₃. These experimental and computational results are broadly impactful because they reach into the thin-film and theoretical communities who have shown that SrVO₃ is a technologically viable transparent conducting oxide material and have used SrVO₃ to develop theoretical methods, respectively.