Exploring charge and spin fluctuations in infinite-layer cuprate SrCuO${}_2$ from a phonon perspective

Abstract

The infinite-layer cuprate $A$CuO${}_2$ ($A=$ Ca, Sr, Ba) has the simplest crystal structure among numerous cuprate superconductors and can serve a prototypical system to explore the unconventional superconductivity. Based on the first-principles electronic structure calculations, we have studied the electronic and magnetic properties of the infinite-layer cuprate SrCuO${}_2$ from a phonon perspective. We find that interesting fluctuations of charges, electrical dipoles, and local magnetic moments can be induced by the zero-point vibrations of phonon modes in SrCuO${}_2$ upon the hole doping. Among all optical phonon modes of SrCuO${}_2$ in the antiferromagnetic Néel state, only the $A_1$${}_g$ mode that involves the full-breathing O vibrations along the Cu-O bonds can cause significant fluctuations of local magnetic moments on O atoms and dramatic charge redistributions between Cu and O atoms. Notably, due to the zero-point vibration of the $A_{1g}$ mode, both the charge fluctuations on Cu and the electrical dipoles on O show a dome-like evolution with increasing hole doping, quite similar to the experimentally observed behavior of the superconducting $T_c$; in comparison, the fluctuations of local magnetic moments on O display a monotonic enhancement along with the hole doping. Further analyses indicate that around the optimal doping, there exist a large softening in the frequency of the $A_{1g}$ phonon mode and a van Hove singularity in the electronic structure close to the Fermi level, suggesting potential electron-phonon coupling. Our work reveals the important role of the full-breathing O phonon mode playing in the infinite-layer SrCuO${}_2$, which may provide new insights in understanding the cuprate superconductivity.

7 pages, 4 figures, 1 table

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Cited by in corpus (2)

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• Origin of insulating-like behavior of Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+x}$ under pressure: A first-principles study