Superconducting critical temperature and dimensionality tuning of RbV3Sb5 via biaxial strain

Kagome metal AV3Sb5 (A = K, Rb, Cs) has emerged as an intriguing platform for exploring the interplay between superconductivity and other quantum states. Among the three compounds, RbV3Sb5 has a notably lower superconducting critical temperature (Tc) at ambient pressure, posing challenges in exploring the superconducting state. For instance, the upper critical field (Hc2) is small and thus difficult to measure accurately against other control parameters. Hence, enhancing superconductivity would facilitate Hc2 measurements, providing insights into key superconducting properties such as the dimensionality. In this Letter, we report the tuning of the Tc in RbV3Sb5 through the application of biaxial strain. Utilizing a negative thermal expansion material ZrW2O8 as a substrate, we achieve a substantial biaxial strain of ɛ = 1.50%, resulting in a remarkable 75% enhancement in Tc. We investigate the Hc2 as a function of temperature, revealing a transition from multi-band to single-band superconductivity with increasing tensile strain. In addition, we study the Hc2 as a function of field angle, revealing a plausible correlation between the Tc enhancement and the change in dimensionality of the superconductivity under tensile strain. Further analysis quantitatively illustrates a transition toward two-dimensional superconductivity in RbV3Sb5 when subjected to tensile strain. Our work demonstrates that the application of biaxial strain allows for the tuning of both the Tc and superconducting dimensionality in RbV3Sb5.