Hidden Orbital Order in Quantum Kagome Metals

The kagome metals AV₃Sb₅ (A = K, Rb, Cs) offer a fascinating playground for exploring the complex behavior of interacting electrons — one of the central challenges in modern condensed matter physics. A key open question is which structural and electronic degrees of freedom govern their unusual properties and how these are intertwined.

In our recent study, we addressed this question by investigating how the electronic superlattices in CsV₃Sb₅ respond to minute mechanical strain. Using our high-resolution x-ray facility VEGA, we uncovered a gigantic strain sensitivity of the 2×2×4 electronic crystal, demonstrating how its domains can be tuned and controlled. Interestingly, the competing 2×2×2 order exhibits a strikingly different behavior, remaining essentially unaffected by uniaxial strain.

Combining these observations with density functional theory, we find that the pronounced strain response originates from V-3d orbital order, highlighting the active role of orbital degrees of freedom in shaping the low-energy physics. These results open new avenues for understanding and controlling emergent quantum orders in kagome materials.

Check out our preprint for more information!