# Shot-noise spectroscopy links the pseudogap in Bi2Sr2CaCu2O8+δ to electron pairs, up to 70 meV

- Published: 2026-11-07 18:58 UTC
- Section: Science › Physics
- Tags: pseudogap, cuprate superconductors, Bi2Sr2CaCu2O8+δ, Cooper pairs, shot-noise spectroscopy, phase coherence, high-temperature superconductivity, scanning tunnelling microscopy
- URL: https://realtech.media/news/rt-04d6a2261233235806872a74_shot_noise_spectroscopy/

**Groups from Munich, Utrecht and Leiden used local shot-noise measurements on a cuprate: the pseudogap energy matches the onset of electron pairing.**

![Shot-noise spectroscopy links the pseudogap in Bi2Sr2CaCu2O8+δ to electron pairs, up to 70 meV](https://realtech.media/media/2026/11/2e6a1313d123e7f9.png)
*ingenieur.de*

Researchers from Munich, Utrecht and Leiden reported local shot-noise spectroscopy measurements on the cuprate Bi2Sr2CaCu2O8+δ. The work was published on 5 November 2026 in Science. According to the authors, the pseudogap energy coincides with the onset of electron pairing and varies from place to place in the sample, reaching up to 70 meV [1].

## Pseudogap and competing explanations

The pseudogap is a state in which the number of available electronic states in a certain energy range is reduced. It stands out in the phase diagram of cuprate high-temperature superconductors, because its origin and its relation to superconductivity remain unclear [1]. One hypothesis attributes it to preformed electron pairs. Others link it to local order, such as charge density waves [1].

The authors state that their data support the pairing scenario. They report that the results exclude a purely local-order origin of the pseudogap and link it to Cooper pair formation [1]. The material shows features reminiscent of a superconductor in this state, but its electrical resistance does not yet vanish.

## Method and open questions

The team used a special form of scanning tunnelling microscopy and recorded small fluctuations of the tunnelling current, known as shot noise. These fluctuations allow the effective charge involved in transport to be determined: a single electron carries one elementary charge, a Cooper pair twice that. This makes it possible to tell whether electrons or pairs contribute to the measured current, with high spatial resolution. Key parts of the apparatus were built for this study.

Based on the data, the authors suggest that the limiting factor for a higher critical temperature in cuprates is phase coherence [1]. Until the pairs form a common superconducting state, the material retains electrical resistance. The researchers also estimate that the pairing energy could in principle be enough for pairs to persist at room temperature.

This is a conclusion drawn from the measurements. The study did not demonstrate superconductivity at room temperature, nor how the required phase coherence could be established there. The role of the pseudogap is still debated: a Nature Physics study from October 2026 reports indications that the pseudogap state and superconductivity can compete under certain conditions. The group plans to examine which processes prevent phase coherence.

## Sources

1. [Science](https://doi.org/10.1126/science.adt3444)
2. [ingenieur.de](https://www.ingenieur.de/strom-ohne-widerstand-forscher-loesen-teil-eines-grossen-physikraetsels-b034dc02-8dff-4dda-be78-4de1e16039a4)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-04d6a2261233235806872a74_shot_noise_spectroscopy/