Carrier Density Dependence of Superconducting Transition Temperature in Electron-doped $\rm{SrTiO_3}$ Based on the First-principles Calculations
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| Main Authors: | , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866915494723846144 |
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| author | Ikaida, Riku Sano, Kazuhiro Masuda, Yoshimi Sekikawa, Takuya Ōno, Yoshiaki |
| author_facet | Ikaida, Riku Sano, Kazuhiro Masuda, Yoshimi Sekikawa, Takuya Ōno, Yoshiaki |
| contents | Electron-doped strontium titanate $\rm{SrTiO_3}$, known to be one of the most dilute superconductors, is investigated on the basis of the first-principles calculations. When the carrier density n decreases, the frequencies of the ferroelectric optical phonons near the $Γ$-point monotonically decreases in the overdoped regime with $n<10^{20}/\rm{cm}^{3}$, while unphysical imaginary phonon frequencies due to ferroelectric instabilities appear in the underdoped regime with $n>10^{20}/\rm{cm}^{3}$. We estimate the superconducting transition temperature $T_{\rm{c}}$ by using the McMillan equation in the overdoped regime and find that $T_{\rm{c}}$ increases with decreasing n as consistent with experiments in the overdoped regime. Detailed analysis of the Eliashberg function reveals that the increases in $T_{\rm{c}}$ with decreasing n in the overdoped regime is mainly due to the contributions from the ferroelectric soft-mode optical phonons. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2509_10881 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Carrier Density Dependence of Superconducting Transition Temperature in Electron-doped $\rm{SrTiO_3}$ Based on the First-principles Calculations Ikaida, Riku Sano, Kazuhiro Masuda, Yoshimi Sekikawa, Takuya Ōno, Yoshiaki Superconductivity Electron-doped strontium titanate $\rm{SrTiO_3}$, known to be one of the most dilute superconductors, is investigated on the basis of the first-principles calculations. When the carrier density n decreases, the frequencies of the ferroelectric optical phonons near the $Γ$-point monotonically decreases in the overdoped regime with $n<10^{20}/\rm{cm}^{3}$, while unphysical imaginary phonon frequencies due to ferroelectric instabilities appear in the underdoped regime with $n>10^{20}/\rm{cm}^{3}$. We estimate the superconducting transition temperature $T_{\rm{c}}$ by using the McMillan equation in the overdoped regime and find that $T_{\rm{c}}$ increases with decreasing n as consistent with experiments in the overdoped regime. Detailed analysis of the Eliashberg function reveals that the increases in $T_{\rm{c}}$ with decreasing n in the overdoped regime is mainly due to the contributions from the ferroelectric soft-mode optical phonons. |
| title | Carrier Density Dependence of Superconducting Transition Temperature in Electron-doped $\rm{SrTiO_3}$ Based on the First-principles Calculations |
| topic | Superconductivity |
| url | https://arxiv.org/abs/2509.10881 |