Scientists at the University of California, Irvine have uncovered the atomic-scale mechanics that enhance superconductivity in an iron-based material, a finding published recently in Nature.
Using advanced spectroscopy instruments housed in the UC Irvine Materials Research Institute, the researchers were able to image atom vibrations and thereby observe new phonons—quasiparticles that carry thermal energy—at the interface of an iron selenide (FeSe) ultrathin film layered on a strontium titanate (STO) substrate.
“Primarily emerging from the out-of-plane vibrations of oxygen atoms at the interface and in apical oxygens in STO, these phonons couple with electrons due to the spatial overlap of electron and phonon wave functions at the interface,” said lead author Xiaoqing Pan, UC Irvine Distinguished Professor of materials science and engineering, Henry Samueli Endowed Chair in Engineering and IMRI director.
“This strong electron-phonon coupling provides a mechanism for the enhancement of superconductivity transition temperature in ultrathin FeSe.”
The scientists found that FeSe has a transition-to-superconductivity temperature of 65 Kelvin, roughly minus 340 degrees Fahrenheit, making it the highest-temperature superconductor in its class. They witnessed a close relationship between electron-phonon coupling and the uniformity of the FeSe/STO interface; greater homogeneity means a higher temperature at which superconductivity occurs.
“Our vibrational spectroscopy approach enabled us to achieve highly detailed imaging of the vibrations at the superconducting material’s interface with its substrate,” said Pan, who holds a joint appointment in the UC Irvine Department of Physics & Astronomy.
“The observed variation in the interlayer spacing correlates with the superconducting gap, which demonstrates the crucial role of spacing in electron-phonon coupling strength and superconductivity.”
Co-author Ruqian Wu, UC Irvine Distinguished Professor of physics and astronomy, said, “The ultrahigh spatial and energy resolutions of state-of-the-art instruments at IRMI provide exceptional experimental data for theoretical analysis. This collaboration between theoretical simulations and experimental observations allows for precise identification of individual atomic contributions to the enhancement of the superconducting transition temperature, deepening our understanding of superconductivity at heterogeneous interfaces.”
Pan said that his team’s results are an important step toward achieving scalable fabrication and utilization of superconductors in a range of applications, including quantum computers, mass transportation through magnetic levitation, and advanced medical diagnostic and treatment devices.
More information:
Hongbin Yang et al, Phonon modes and electron–phonon coupling at the FeSe/SrTiO3 interface, Nature (2024). DOI: 10.1038/s41586-024-08118-0
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University of California, Irvine
Citation:
Scientists reveal superconductivity secrets of an iron-based material (2024, December 5)
