Scientists reveal the secret of superconductivity in iron-based materials

Scientists at the University of California, Irvine have uncovered the atomic-scale mechanics that make iron-based materials superconducting, a discovery recently published in Nature.

Using state-of-the-art spectroscopic equipment at the University of California, Irvine Materials Research Institute, the researchers imaged the vibrations of atoms at the interface of an ultrathin film of iron selenide (FeSe) layered on strontium titanate. We were able to observe a new phonon (a quasiparticle that carries thermal energy). (STO) Substrate.

“These phonons, which mainly emerge from the out-of-plane vibrations of oxygen atoms at the interface and apical oxygen of the STO, couple with electrons due to the spatial overlap of the electron and phonon wave functions at the interface,” said first author Xiaoqing Pan. said. , Distinguished Professor of Materials Science and Engineering, Henry Samueli Endowed Chair in Engineering, and Director of IMRI, University of California, Irvine.

“This strong electron-phonon coupling provides a mechanism to increase the superconducting transition temperature of ultrathin FeSe.”

Scientists discovered that FeSe has a superconducting transition temperature of 65 Kelvin (about minus 340 degrees Fahrenheit), making it the hottest superconductor in its class. They demonstrated that there is a close relationship between electron–phonon coupling and the uniformity of the FeSe/STO interface. High homogeneity means a high temperature at which superconductivity occurs.

“With our vibrational spectroscopy approach, we were able to achieve very detailed imaging of vibrations at the interface of a superconducting material and its substrate,” said Pan, who also holds a joint appointment with the Department of Physics and Astronomy at the University of California, Irvine. he said.

“The observed interlayer spacing changes are correlated with the superconducting gap, indicating the important role of spacing in electron-phonon coupling strength and superconductivity.”

“The ultra-high spatial and energy resolution of IRMI’s state-of-the-art instruments will provide excellent experimental data for theoretical analysis,” said co-author Ruqian Wu, Distinguished Professor of Physics and Astronomy at the University of California, Irvine. This collaboration of theoretical simulations and experiments allows us to pinpoint the contribution of individual atoms to the increase in superconducting transition temperature, deepening our understanding of superconductivity at heterogeneous interfaces.”

Pan said his team’s work is an important step toward achieving scalable manufacturing and use of superconductors in a variety of applications, including quantum computers, magnetic levitation mass transportation, and advanced medical diagnostic and therapeutic devices. He said it would be.