Uniaxial stress enhanced anisotropic magnetoresistance and superconductivity in the kagome superconductor LaRu${}_3$Si${}_2$

Abstract

Elucidating the role of the kagome electronic structure in determining the various quantum ground states is of fundamental importance. In this work, we employ in-plane uniaxial stress as a tuning parameter to probe the electronic structure and its impact on the superconducting and normal-state properties of the kagome superconductor LaRu${}_3$Si${}_2$, combining magnetotransport measurements with first-principles calculations. We identify a pronounced anisotropy in both the upper critical field and the normal-state magnetoresistance, indicating strong electronic anisotropy despite the three-dimensional crystal structure. Furthermore, we find that the superconducting transition temperature $T_{\mathrm{c}}$ increases under in-plane stress applied within the kagome plane, although the enhancement is modest, reaching approximately 0.3 K at 0.6 GPa. Furthermore, the absolute magnetoresistance exhibits a pronounced increase from about 22$\%$ at zero stress to 35$\%$ at 0.6 GPa, indicating a substantial modification of the normal state above $T_{\mathrm{c}}$. Previous studies have reported time-reversal-symmetry (TRS) breaking below a temperature scale that coincides with the onset of magnetoresistance. The simultaneous enhancement of both $T_{\mathrm{c}}$ and magnetoresistance under stress therefore suggests a positive correlation between superconductivity and normal-state electronic and magnetic properties in LaRu${}_3$Si${}_2$. Detailed calculations demonstrate that stress-induced changes in $T_{\mathrm{c}}$ arise from the joint evolution of the total density of states and the flat band, whereas the large magnetoresistance enhancement is dominated by the stress-driven downward shift of the Ru $d{z}^2$ kagome flat band.

8 pages, 4 figures