The effect of epitaxial strain on electron-phonon coupling and superconducting properties of nitride superconductors from first principles

Nitride superconductors offer a unique combination of large superconducting gaps, chemical robustness, and demonstrated integration with industrially capable semiconductors. Recent all-epitaxial integration of niobium nitride superconductors with the III-Nitride family of semiconductors (e.g gallium nitride) has created an opportunity for scalable, integrated superconductor/semiconductor devices with access to industrial fabrication processes.

Niobium nitride has a large superconducting critical temperature, however, its structural, metallic, and superconducting properties are extremely sensitive to growth conditions and nitrogen concentration. In contrast, the Group IVB-Nitrides like titanium nitride, are less growth-condition-sensitive, but their critical temperatures are markedly smaller. Leveraging the epitaxial integration of transition metal nitrides with III-Nitrides, we use first-principles calculations to explore the effect of strain on the electron-phonon coupling and superconducting transition temperature of transition metal nitrides, a potential pathway for tailored superconducting properties.