Enhanced superconductivity in highly compressed vanadium driven by dynamical screened Coulomb interaction

The pressure-driven enhancement of superconducting critical temperature (T_c)​ in transition metals is commonly ascribed to s–d electron transfer. Yet this phenomenological picture lacks a solid microscopic foundation and has recently been called into question. Elemental vanadium, with its 3d³4s² configuration and chemical simplicity, offers an ideal platform to elucidate the underlying mechanism. Here, we performed electrical transport measurements of superconductivity and X-ray diffraction up to 283 GPa. Electrical transport measurements expand the superconducting phase diagram, revealing a highest T_c of 20.9 K at 265 GPa. X-ray diffraction measurements show a gradual distortion of the body-centered cubic structure and the emergence of a rhombohedral phase above 200 GPa. Combined experimental results and first-principles calculations indicate that dynamical electron-electron interactions, rather than the widely accepted s–d electron transfer scenario, are crucial to understand the pressure-induced enhancement of T_c​ in this system. These findings suggest limitations of the static approximation for the screened electron-electron interactions commonly used in current implementations of the density-functional theory for superconductors.