Ambient-pressure superconductivity above 22 K in hole-doped YB2

Abstract: Recent studies of hydrogen-dominant (superhydride) materials, such as LaH10 have led to putative discoveries of near-room temperature superconductivity at high pressures, with a superconducting transition temperature (Tc) of 250 K observed at 170 GPa. While these findings are promising, achieving such high superconductivity requires challenging experimental conditions typically exceeding 100 GPa. In this study, we utilize first-principles calculations and Migdal-Eliashberg theory to examine the superconducting properties of the stable boron-based compound YB2 at atmospheric pressure, where yttrium and boron atoms form a layered structure. Our results indicate that YB2 exhibits a Tc of 2.14 K at 0 GPa. We find that doping with additional electrons (0 to 0.3) leads to a monotonic decrease in Tc as the electron concentration increases. Conversely, introducing holes significantly enhances Tc, raising it to 22.83 K. Although our findings do not surpass the superconducting temperature of the well-known MgB2, our doping strategy highlights a method for tuning electron-phonon coupling strength in metal borides. This insight could be valuable for future experi-mental applications. Overall, this study not only deepens our understanding of YB2 superconducting properties but also contributes to the ongoing search for high-temperature superconductors.