Calculations of Spin Fluctuation Spectral Functions $α^{2}F$ in High-Temperature Superconducting Cuprates
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| Format: | Preprint |
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2024
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| _version_ | 1866908321431158784 |
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| author | Heier, Griffin Savrasov, Sergey Y. |
| author_facet | Heier, Griffin Savrasov, Sergey Y. |
| contents | Spin fluctuations have been proposed as a key mechanism for mediating superconductivity, particularly in high-temperature superconducting cuprates, where conventional electron-phonon interactions alone cannot account for the observed critical temperatures. Traditionally, their role has been analyzed through tight-binding based model Hamiltonians. In this work we present a method that combines density functional theory with a momentum- and frequency-dependent pairing interaction derived from the Fluctuation Exchange (FLEX) type Random Phase Approximation (FLEX-RPA) to compute Eliashberg spectral functions $α^{2}F(ω)$ which are central to spin fluctuation theory of superconductivity. We apply our numerical procedure to study a series of cuprates where our extracted material specific $α^{2}F(ω)$ are found to exhibit remarkable similarities characterized by a sharp peak in the vicinity of 40-60 meV and their rapid decay at higher frequencies. Our exact diagonalization of a linearized BCS gap equation extracts superconducting energy gap functions for realistic Fermi surfaces of the cuprates and predicts their symmetry to be $d_{x^{2}-y^{2}}$ in all studied systems. Via a variation of on-site Coulomb repulsion $U$ for the copper $d$-electrons we show that that the range of the experimental values of $T_{c}$ can be reproduced in this approach but is extremely sensitive to the proximity of the spin density wave instability. These data highlight challenges in building first-principle theories of high temperature superconductivity but offer new insights beyond previous treatments, such as the confirmation of the usability of approximate BCS-like $T_{c}$ equations, together with the evaluations of the material specific coupling constant $λ$ without reliance on tight-binding approximations of their electronic structures. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2411_06537 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Calculations of Spin Fluctuation Spectral Functions $α^{2}F$ in High-Temperature Superconducting Cuprates Heier, Griffin Savrasov, Sergey Y. Superconductivity Strongly Correlated Electrons Spin fluctuations have been proposed as a key mechanism for mediating superconductivity, particularly in high-temperature superconducting cuprates, where conventional electron-phonon interactions alone cannot account for the observed critical temperatures. Traditionally, their role has been analyzed through tight-binding based model Hamiltonians. In this work we present a method that combines density functional theory with a momentum- and frequency-dependent pairing interaction derived from the Fluctuation Exchange (FLEX) type Random Phase Approximation (FLEX-RPA) to compute Eliashberg spectral functions $α^{2}F(ω)$ which are central to spin fluctuation theory of superconductivity. We apply our numerical procedure to study a series of cuprates where our extracted material specific $α^{2}F(ω)$ are found to exhibit remarkable similarities characterized by a sharp peak in the vicinity of 40-60 meV and their rapid decay at higher frequencies. Our exact diagonalization of a linearized BCS gap equation extracts superconducting energy gap functions for realistic Fermi surfaces of the cuprates and predicts their symmetry to be $d_{x^{2}-y^{2}}$ in all studied systems. Via a variation of on-site Coulomb repulsion $U$ for the copper $d$-electrons we show that that the range of the experimental values of $T_{c}$ can be reproduced in this approach but is extremely sensitive to the proximity of the spin density wave instability. These data highlight challenges in building first-principle theories of high temperature superconductivity but offer new insights beyond previous treatments, such as the confirmation of the usability of approximate BCS-like $T_{c}$ equations, together with the evaluations of the material specific coupling constant $λ$ without reliance on tight-binding approximations of their electronic structures. |
| title | Calculations of Spin Fluctuation Spectral Functions $α^{2}F$ in High-Temperature Superconducting Cuprates |
| topic | Superconductivity Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2411.06537 |