Limitations of probing field-induced response with STM
Summary
Candelora and Zeljkovic comment on recent STM-based claims of magnetic- and light-driven changes to the 2 × 2 charge-density-wave (CDW) and in-plane lattice constants in the kagome superconductor RbV3Sb5. The authors show that the apparent ~1% field-induced lattice change and concomitant CDW intensity modulation reported previously can be reproduced by two experimental artefacts: reconfiguration of the STM tip apex (which alters apparent CDW amplitudes) and instrumental issues such as piezo creep, hysteresis and thermal drift that distort topographs. They argue these artefacts can account for the reported piezomagnetism, and that the effect may not be intrinsic to the sample.
Key Points
- Xing et al. reported magnetic- and light-controlled changes in CDW intensity and a ~1% change in in-plane lattice constants in RbV3Sb5.
- Candelora & Zeljkovic identify two independent experimental artefacts that mimic these effects: tip-apex reconfiguration and piezo/drift distortions.
- Tip changes (double tips, altered impurity appearance, disappearing QPI ring) modify Fourier-transform signals and apparent CDW amplitudes.
- Piezo creep, hysteresis and thermal drift produce artificial stretching/sloping of lattices and inconsistent Bragg/ CDW peak changes between forward and backward scans.
- Extended data show clear scan-to-scan inconsistencies and regions with tip instability; these correlate with the claimed field-dependent switching.
- The authors conclude that the reported piezomagnetic signature is plausibly an experimental artefact rather than an intrinsic field-induced lattice response.
Content summary
The comment carefully re-analyses STM topographs used in the prior work and presents extended-data figures illustrating raw topographs, Fourier transforms and Bragg/CDW peak analysis. It highlights cases where the tip becomes effectively double or otherwise unstable, which changes the apparent number and shape of impurities and erases QPI features. It also documents piezo-related distortions (creep, hysteresis) and thermal drift that lead to non-physical changes in measured lattice lengths and intensities. Where the original study reports consistent switching of particular Bragg peak amplitudes with magnetic-field direction, the re-analysis finds inconsistencies between forward and backward scans and large variations that align with instrument artefacts rather than a clean intrinsic effect.
The authors provide a clear methodological caution: STM is extremely sensitive to tip condition and scanner nonlinearities, and small uncorrected instrumental effects can masquerade as subtle, field-induced structural responses.
Context and relevance
Kagome superconductors AV3Sb5 (A = K, Rb, Cs) are a hot topic because of intertwined density waves, unconventional superconductivity and reported time-reversal-symmetry breaking. STM is widely used to probe these materials at the atomic scale, so claims of magnetic-field-driven lattice or CDW switching would be important for theory and experiment alike. This comment matters because it forces the community to re-evaluate whether subtle, high-impact claims (for example, field-induced piezomagnetism or lattice distortions) could instead arise from routine STM artefacts. The paper therefore contributes to rigour in experimental practice and to correct interpretation of STM data in correlated materials research.
Why should I read this
Short and simple: if you care about claims from STM that small fields or light change a lattice or CDW, read this. It’s a practical wake-up call — tip oddities and sneaky piezo/drift effects can easily fool you. The authors have done the legwork so you don’t waste time chasing a phantom physical effect.
Source
Article Date: 25 February 2026
Article URL: https://www.nature.com/articles/s41586-026-10126-1
Article Title: Limitations of probing field-induced response with STM
Article Image: Extended Data Fig. 1 (example)