Double-dome superconductivity under pressure in the V-based kagome metals AV3Sb5 (A = Rb and K)

We present high-pressure resistance measurements on the newly discovered V-based superconductors AV3Sb5 (A = Rb and K), which have an ideal kagome lattice of vanadium. Two superconducting domes under pressure are observed in both compounds, as previously observed in their sister compound CsV3Sb5. For RbV3Sb5, the Tc increases from 0.93 K at ambient pressure to a maximum of 4.15 K at 0.38 GPa in the first dome. The second superconducting dome has the highest Tc of 1.57 K at 28.8 GPa. KV3Sb5 displays a similar double-dome phase diagram, however, its two maximum Tcs are lower, and the Tc drops faster in the second dome than RbV3Sb5. An integrated temperature-pressure phase diagram of AV3Sb5 (A = Cs, Rb, and K) is constructed, showing that the ionic radius of the intercalated alkali-metal atoms has a significant effect. Our work demonstrates that double-dome superconductivity under pressure is a common feature of these V-based kagome metals.