Stoichiometric FeTe is a superconductor | Nature

## Summary
Article ADS CAS PubMed Google Scholar Ma, F., Ji, W., Hu, J., Lu, Z. Article ADS CAS PubMed Google Scholar Liang, J. et al. Article ADS CAS PubMed PubMed Central Google Scholar Yi, H. et al. Article ADS CAS PubMed Google Scholar Uehara, Y., Fujita, T., Iwami, M. & Ushioda, S.

## Article Content
Subjects
Magnetic properties and materials
Superconducting properties and materials
Surfaces, interfaces and thin films
Abstract
Iron-based superconductors (FeSCs) are a fascinating family of materials in which several electronic bands and strong antiferromagnetic (AFM) correlations are key ingredients for competing ground states
1
,
2
,
3
,
4
,
5
,
6
, including antiferromagnetism, electronic nematicity and unconventional superconductivity. FeTe, unlike its superconducting isostructural counterpart FeSe, has long been considered an AFM metal sans superconductivity
7
,
8
,
9
. Here we use molecular-beam epitaxy (MBE) to grow FeTe films and perform post-growth annealing under a Te flux. By performing spin-polarized scanning tunnelling microscopy and spectroscopy (STM/S), we demonstrate that the AFM order in as-grown FeTe films is induced by interstitial Fe atoms that disrupt the ideal 1:1 stoichiometry. Notably, the removal of these interstitial Fe atoms through Te annealing yields stoichiometric FeTe films that show no AFM order and instead exhibit robust superconductivity with a critical temperature of about 13.5 K. This superconducting state is further confirmed by the observation of Cooper-pair tunnelling, zero electrical resistance and the Meissner effect. Therefore, our results demonstrate that stoichiometric FeTe is inherently a superconductor, overturning a long-held view that it is an AFM metal. This work clarifies the origin of superconductivity in FeTe-based heterostructures
10
,
11
,
12
,
13
,
14
,
15
and demonstrates the importance of stoichiometry control in understanding the competition between antiferromagnetism and superconductivity in FeSCs.
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Fig. 1: MBE-grown FeTe films before and after Te-annealing treatments.
Fig. 2: Te-annealing treatments on as-grown FeTe films.
Fig. 3: Superconductivity in stoichiometric FeTe films.
Fig. 4: Zero-resistance state and Meissner effect in stoichiometric FeTe films.
Data availability
The data that support the findings of this article are openly available at Zenodo
61
(
https://doi.org/10.5281/zenodo.17944465
).
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Yi, H. et al. Int

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## Expert Analysis

### Merits
- Subjects Magnetic properties and materials Superconducting properties and materials Surfaces, interfaces and thin films Abstract Iron-based superconductors (FeSCs) are a fascinating family of materials in which several electronic bands and strong antiferromagnetic (AFM) correlations are key ingredients for competing ground states 1 , 2 , 3 , 4 , 5 , 6 , including antiferromagnetism, electronic nematicity and unconventional superconductivity.
- Notably, the removal of these interstitial Fe atoms through Te annealing yields stoichiometric FeTe films that show no AFM order and instead exhibit robust superconductivity with a critical temperature of about 13.5 K.

### Areas for Consideration
N/A

### Implications
- Go to natureasia.com Buy this article Purchase on SpringerLink Instant access to the full article PDF. 39,95 € Prices may be subject to local taxes which are calculated during checkout Fig. 1: MBE-grown FeTe films before and after Te-annealing treatments.

### Expert Commentary
This article covers article, google, scholar topics. Notable strengths include discussion of article. Readability: Flesch-Kincaid grade 0.0. Word count: 2370.