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Loop currents have been proposed as the origin of the pseudogap phase in the cuprate high-temperature superconductors, have been connected to the CDW phase of Kagome materials and proposed to occur at the surface layer of Sr₂RuO₄. These loop currents are extremely hard to detect, as they produce only tiny local magnetic fields. STM, being a local experimental technique, has been proposed as a way to detect them. In our recent preprint, we make realistic predictions for the signatures that loop currents would create in an STM experiment. Using our calcQPI code, we show that loop currents, in the presence of spin-orbit coupling, give rise to a spin polarization with a large enough signal to be detected by spin-polarized STM.

• V. Morisseau, L. C. Rhodes, P. Wahl, C. A. Marques, “How to measure loop currents in scanning tunneling microscopy”, arXiv:2607.20030 (2026).

Does the surface layer of an itinerant ferromagnet change its magnetization direction at the same field as the bulk? Not always – at least not in Sr₄Ru₃O₁₀. Domain wall pinning allows us to precisely control the magnetic configuration of surface and bulk. Using scanning tunneling microscopy at ultra-low temperatures, Carolina Marques found how the electronic states change between ferromagnetic and antiferromagnetic alignment of the surface layer and bulk magnetizations. Intriguingly, through control of the magnetic configuration, we were able to detect the tiny structural change that accompanies the change in magnetic configuration. While tiny in the grand scheme of things, our measurements reveal a giant magnetoelastic coupling that is driven by exchange interactions, qualitatively as expected from the Bethe-Slater curve sketched almost a century ago. Our results highlight the coupling between electronic, magnetic and structural degrees of freedom, and how these effects are enhanced through electronic correlations.

Read more in our publication at:

• Carolina A. Marques, Luke C. Rhodes, Weronika Osmolska, Harry Lane, Izidor Benedičič, Masahiro Naritsuka, Siri A. Berge, Rosalba Fittipaldi, Mariateresa Lettieri, Antonio Vecchione, and Peter Wahl, Emergent exchange-driven giant magnetoelastic coupling in a correlated itinerant ferromagnet, Nat. Phys. 21, 1243 (2025).