Dome-Shaped Superconducting Phase Diagram Linked to Charge Order in LaRu$_{3}$Si$_{2}$

TL;DR

This study reveals a dome-shaped relationship between superconductivity and charge order in LaRu$_{3}$Si$_{2}$ under pressure, showing that superconductivity peaks when charge order is optimized, highlighting a close interdependence unlike in other materials.

Contribution

The paper uncovers a pressure-induced dome-shaped phase diagram linking superconductivity and charge order in LaRu$_{3}$Si$_{2}$, demonstrating their interdependence and contrasting with other known systems.

Findings

Superconducting transition temperature $T_c$ peaks at 9 K around 2 GPa.

Charge order transitions shift from long-range to short-range above 12 GPa.

Superconductivity correlates with the charge-ordered state, peaking when charge order is optimized.

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$_{2}$ ($T_{\rm c}$ ${\simeq}$ 6.5 K) exhibits a hierarchy of charge order transitions: primary ($T_{\rm co,I}$ ${\simeq}$ 400 K), secondary ($T_{\rm co,II}$ ${\simeq}$ 80 K), and an additional transition at ($T^{*}$ $\simeq$ 35 K). The transitions at $T_{\rm co,II}$ and $T^{*}$ 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 $T_{\rm c}$ 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 $T^{*}$ 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 $T_{\rm c}$, suggesting superconductivity is closely tied to the charge-ordered state. Specifically, $T_{\rm c}$ 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.