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Innovative Approach to Investigating Disorder in Superconductors
A collaboration between researchers at the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany, and Brookhaven National Laboratory in the United States has introduced a novel technique for examining disorder within superconductors, utilizing terahertz light pulses.
This study, published in Nature Physics, adapts methodologies from nuclear magnetic resonance to the realm of terahertz spectroscopy. For the first time, the team tracked disorder evolution in the electronic transport properties of superconductors as they approached the transition temperature.
Understanding the role of disorder in physical systems presents significant challenges. High-temperature superconductors, which function at temperatures near -170°C, heavily rely on chemical compositions that introduce variations, yet the precise effects of these variations on their superconducting characteristics remain poorly understood.
Traditionally employed techniques, such as scanning tunneling microscopy, only function under extreme cold conditions. They also struggle to detect disorder phenomena as the superconducting transition temperature nears, limiting our understanding of these critical systems.
Superconductivity is a key focus within condensed matter physics, recognized for its potential to facilitate lossless electrical current flow, impacting numerous technological domains. The complexity of high-temperature superconductors, notably the cuprate class, stems from their reliance on chemical doping, which generates inherent disorder.
Disorder studies in superconductors typically involve advanced experiments that achieve high spatial resolution through sharp metallic tips. However, the sensitivity required for such probes confines their application to temperatures well below the superconducting transition point, leaving numerous essential questions unaddressed.
The research team drew inspiration from sophisticated multi-dimensional spectroscopic methods originally crafted for nuclear magnetic resonance studies. These methods had been adapted in the past for visible and ultraviolet light application in chemical and biological systems. The MPSD team successfully translated these techniques to the terahertz frequency spectrum, where solid materials exhibit collective resonant modes.
In their investigation of the cuprate superconductor La1.83Sr0.17CuO4, a material characterized by its opacity and minimal light transmission, the researchers pioneered the application of two-dimensional terahertz spectroscopy (2DTS) in a non-collinear arrangement. This innovation allowed them to distinguish specific terahertz nonlinearities based on their emission direction.
Through the angle-resolved 2DTS method, the team discovered that the superconducting transport properties of the cuprates were enhanced following excitation by terahertz pulses, an effect named “Josephson echoes.” Unexpectedly, these echoes indicated that disorder within the superconducting transport was considerably less than the disorder measured in the superconducting gap by conventional spatially resolved techniques.
Additionally, the angle-resolved 2DTS method allowed for unprecedented measurements of disorder near the superconducting transition temperature, revealing a remarkable stability of this disorder up to 70% of the transition temperature.
The findings not only advance understanding of cuprate superconductors but also pave the way for future research avenues. The flexibility of angle-resolved 2DTS holds promise for application across various superconductors and quantum materials, as its ultrafast capabilities enable the investigation of transient matter states that are transiently beyond the reach of standard disorder probes.
More information:
A. Liu et al, Probing inhomogeneous cuprate superconductivity by terahertz Josephson echo spectroscopy, Nature Physics (2024). DOI: 10.1038/s41567-024-02643-5.
Citation:
Research team uses terahertz pulses of light to shed light on superconducting disorder (2024, September 16) retrieved 16 September 2024 from https://phys.org/news/2024-09-team-terahertz-pulses-superconducting-disorder.html
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phys.org