Stoichiometric FeTe is a superconductor
Summary
This Nature paper reports that stoichiometric FeTe — long thought to be a nonsuperconducting parent compound in the iron-chalcogenide family — exhibits clear superconducting behaviour when grown and processed to remove interstitial iron. The team used molecular-beam epitaxy (MBE) growth and successive Te-annealing cycles to produce 40-unit-cell FeTe films with greatly reduced interstitial-Fe content. Multiple, complementary probes (STM/S including Josephson tunnelling, Abrikosov-vortex imaging, transport, MFM, STEM, AFM and XRD) show superconducting signatures down to millikelvin temperatures, with Josephson peaks and vortices observed by STM/S and a superconducting transition seen in electrical transport. The data and analysis are backed by theoretical support and are openly available on Zenodo.
Key Points
- Stoichiometric FeTe films were prepared by MBE and iterative Te-annealing to remove interstitial Fe that suppresses superconductivity.
- STM/S measurements reveal a superconducting gap and Josephson tunnelling features using a superconducting Nb tip, indicating Cooper-pair tunnelling.
- Abrikosov vortices are imaged in the stoichiometric films, providing direct real-space evidence of bulk superconductivity under applied magnetic field.
- Transport (Rxx–T) measurements show a superconducting transition after annealing cycles that reduce interstitial-Fe density.
- Magnetic and structural characterisation (MFM, STEM, AFM, XRD) confirm the film quality and correlate the suppression of bicollinear antiferromagnetism with the emergence of superconductivity.
- Numerical calculations and theoretical analysis support an impurity-driven picture in which interstitial Fe stabilises magnetic order that otherwise prevents superconductivity.
- All primary data supporting the paper are openly available on Zenodo (https://doi.org/10.5281/zenodo.17944465).
Why should I read this?
Because this flips a long-standing assumption on its head — FeTe itself can superconduct if you get rid of the pesky interstitial iron. If you care about iron-based superconductors, Majorana platforms or material tuning tricks, this is the short cut to the new headline without wading through the full technical detail. Lovely data, neat real-space imaging of vortices and Josephson signals — worth a quick read.
Author style
Punchy: the authors present a tight, multi-technique case that stoichiometry matters more than previously thought for FeTe. This is highly relevant to anyone studying iron-chalcogenide superconductivity or engineering superconducting interfaces — read the methods and SI if you want to reproduce the films.
Context and relevance
This result matters because FeTe has been treated as the non-superconducting partner in Fe(Se,Te) and related systems. Showing that stoichiometric FeTe can become superconducting when interstitial-Fe is removed challenges models that attribute the lack of superconductivity purely to bandstructure and instead highlights the critical role of magnetic impurities and disorder. The finding connects to broader trends in the field: interface-enhanced superconductivity, impurity control by annealing, and the ongoing hunt for platforms that could host topological superconductivity and Majorana modes.