Visualizing melting magnetic order and spin fluctuations in the cuprates

Project Information

SpinMelt

Grant agreement ID: 758572

DOI

10.3030/758572

Project closed

EC signature date 15 September 2017

Start date 1 October 2017

End date 31 January 2023

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 1 847 500,00

EU contribution

€ 1 847 500,00

Coordinated by

UNIVERSITEIT LEIDEN
Netherlands

Periodic Reporting for period 4 - SpinMelt (Visualizing melting magnetic order and spin fluctuations in the cuprates)

Reporting period: 2022-04-01 to 2023-01-31

Summary of the context and overall objectives of the project

Superconductivity is a state of matter in which electrical currents can flow without loss of energy. This is important from a technology point of view (e.g. for the energy transition), as well as from a fundamental physics point of view. In this ERC project, we concentrated on understanding superconductivity.

The aim of the project was to bring new insight and understanding into unconventional superconductors, by building novel, one-of-its-kind instrumentation. We were particularly interested in the curate superconductors, and how higher frequency detection might give insights into their physics. Indeed, we discovered what limits superconductivity in a specific quantum material, which increases our understanding of the word around us, and might pave the way for technological improvements in the future. Other highlights include the development of novel instrumentation, the discovery of a new quantum liquid, and the first imaging of special superconducting puddles.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

For the duration of the SpinMelt ERC project, our team aimed to advance our understanding of unconventional superconductors, primarily through the development and application of advanced instrumentation. This effort led to progress, which was also directed by the insights we gained along the way, prompting deviations from our original trajectory and unexpected results.

A significant portion of our work was devoted to enhancing the STM's higher frequency capabilities – mainly in the regime of microseconds. We did this by introducing the cryogenic high-frequency amplifier. Developing the amplifier was a significant task that took several years, and input from several team members. In the end, the amplifier allowed us to delve deeper into pairing dynamics and explore the phenomenon of charge trapping in unconventional superconductors.

A first important discovery was the identification of a new quantum liquid state in a disordered superconductor. We found that in titanium nitride, electrons are paired even if the materials is not superconducting. This is special: in all conventional metals and insulators, single, non-paired electrons underpin the electronic properties.

A second important outcome stems from our work with scanning Josephson spectroscopy. We were the first to detect nanoscale inhomogeneity in superfluid within an iron-selenium-tellurium compound. This tells us what limits superconductivity in quantum materials.
There were many more findings and instrument developments, which we published along the way.

Throughout the project, we made our findings accessible, publishing in prominent (and less prominent) journals and presenting our work at conferences. We aimed to publish all papers in open access journals. We further deposited our data in repositories.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Our work allowed us to go far beyond the state of the art, as expected from an ERC project.

First, there is the instrumentation. We managed to build the best scanning tunnelling microscope (STM) that can measure fluctuations on the microsecond timescale. Using it, we were the first to measure electron pairs on the atomic scale; we call this the "electron pair microscope". We also build nano/micro fabricated tips that can be used for STM.

Second, there are at the scientific break thoughts. They are already mentioned above and in the publication list, so we will have a bit of a helicopter view here.

Quantum materials have been a mystery for decades. It is clear that they hold technological promise, so understanding might help us meet the challenges of today's world from a technology point of view. Also important is the fundamental science part. This ERC allowed us to understand quantum materials better, therefore helping humankind understand the world we live in. To close the circle, we mention that fundamental science will often help future technology in ways that are not expected.

What enabled us go beyond the state of the art is that we build new, custom instrumentation that was build to answer the questions we were interested. For example, the Josephson microscope allowed us to understand the heterogeneity of superconductors, and the electron pair microscope allowed us to discover a new quantum liquid.

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Here, Koen is working on a low-temperature microscope that can measure how electronic states order i

In this ERC project, researcher discovered a quantum liquid that consists of electron pairs without

This image shows a center of enhanced noise, only a few atoms large. This Telles us something about

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