One quantum material, two superconducting states: Stretching helps explain

Unconventional superconductors represent one of the most fascinating frontiers in modern condensed matter physics. These materials exhibit complex electronic behaviors that defy standard theoretical frameworks. Among these phenomena, the coexistence of multiple electronic states often complicates efforts to understand the fundamental mechanisms driving superconductivity. When different types of order compete or cooperate within the same crystal lattice, researchers face significant challenges in isolating the primary driver of zero-resistance electrical transport.

In recent years, the kagome metal CsV3Sb5 has captured the intense attention of the physics community. Named after its distinctive kagome lattice structure, which resembles a traditional Japanese woven basket pattern of corner-sharing triangles, this compound displays a rich interplay of electronic charge order, magnetism, and superconductivity. However, different experimental groups around the world have reported conflicting results regarding its superconducting properties. Some measurements pointed toward one type of pairing symmetry, while other experiments suggested entirely different states, leaving theorists and experimentalists alike searching for a unifying explanation.

To address these discrepancies, a team of researchers investigated how physical manipulation, specifically stretching or applying strain to the material, influences its microscopic behavior. Crystal lattice strain is a powerful tool in materials science because it alters the distances between atoms without changing the overall chemical composition. By gently stretching samples of CsV3Sb5, the scientists were able to tune the delicate balance between competing electronic orders within the kagome structure.

The results of these strain-tuning experiments offer a compelling resolution to the conflicting data collected across various laboratories. The research demonstrates that CsV3Sb5 can host two distinct superconducting states, each favored under slightly different local mechanical conditions. When the crystal lattice is unstrained or experiences compression, one state dominates. Conversely, when the material is subjected to controlled stretching, the electronic landscape shifts, allowing the second superconducting state to emerge and thrive.

This discovery highlights the critical role that microscopic imperfections, sample preparation, and internal stresses play in quantum materials. In many cases, conflicting experimental results do not stem from measurement errors, but rather from subtle variations in how samples are handled or mounted. By explicitly mapping out how strain controls the transition between these two superconducting phases, the new findings provide a reliable roadmap for reconciling past studies and guiding future investigations.

Looking ahead, understanding the interplay between strain and superconductivity in kagome metals opens up exciting possibilities for materials engineering. Researchers can potentially use targeted mechanical stretching or epitaxial strain on thin films to design custom electronic properties on demand. As physicists continue to probe the depths of unconventional superconductivity, materials like CsV3Sb5 serve as vital model systems for unlocking the next generation of advanced electronic technologies.