Universal Fermi velocity in highly compressed hydride superconductors

The Fermi velocity vF is one of the primary characteristics any conductor, including superconductor. For conductors at ambient pressure, several experimental techniques have been developed to measure vF, and, for instance, Zhou et al. [Nature 423, 398 (2003)] reported that high-Tc cuprates exhibited a universal nodal vF,univ=2.7±0.5×105 m/s. However, there no measurements in highly compressed near-room-temperature superconductors (NRTS), owing challenges. Here, answer question existence NRTS materials, we analyze full inventory data on ground-state upper critical field Bc2(0) these materials and find this class exhibits vF,univ=1/1.3×2Δ0/kBTc×105 m/s, where Δ(0) amplitude energy gap. ratio 2Δ0/kBTc varies within narrow range 3.2≤2Δ0/kBTc≤5, so vF,univ lies 2.5 × 105 m/s ≤ 3.8 which similar values found cuprate counterparts materials.