Dome-Shaped Superconducting Phase Diagram Linked to Charge Order in LaRu${}_3$Si${}_2$

Abstract

The interplay between superconductivity and charge order is a central focus in condensed matter research, with kagome lattice systems offering unique insights. The kagome superconductor LaRu${}_3$Si${}_2$ ($T_{\mathrm{c}}$ $\simeq$ 6.5 K) exhibits a hierarchy of charge order transitions: primary ($T_{\mathrm{co},\mathrm{I}}$ $\simeq$ 400 K), secondary ($T_{\mathrm{co},\mathrm{II}}$ $\simeq$ 80 K), and an additional transition at ($T^{\ast }$ $\simeq$ 35 K). The transitions at $T_{\mathrm{co},\mathrm{II}}$ and $T^{\ast }$ are linked to electronic and magnetic responses as revealed by muon-spin rotation and magnetotransport experiments. However, the connection between superconductivity, charge order, and electronic responses has remained elusive. By employing magnetotransport and X-ray diffraction techniques under pressures of up to 40 GPa, we observe that $T_{\mathrm{c}}$ rises to 9 K at 2 GPa, remains nearly constant up to 12 GPa, and then decreases to 2 K at 40 GPa, resulting in a dome-shaped phase diagram. The resistivity anomaly at $T^{\ast }$ and magnetoresistance also exhibit a similar dome-shaped pressure dependence. Furthermore, we find that charge order transitions from long-range to short-range above 12 GPa, correlating with the suppression of $T_{\mathrm{c}}$, suggesting superconductivity is closely tied to the charge-ordered state. Specifically, $T_{\mathrm{c}}$ peaks when charge order and the normal-state electronic responses are optimized. In contrast to systems like the cuprates, transition metal dichalcogenides, and other kagome materials, where superconductivity typically competes with charge order, LaRu${}_3$Si${}_2$ displays a pronounced interdependence between these two phenomena. This distinctive behavior sheds new light on the connection between superconductivity and charge order, offering avenues for theoretical advancements in understanding superconductivity.