<p>We investigate pressure-induced superconductivity in the electride compound Li<sub>5</sub>C and in elemental <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\omega \)</EquationSource> </InlineEquation>-Hf using density functional theory (DFT) combined with Migdal–Eliashberg theory. Despite their distinct chemistry, both systems become superconducting under compression and share a key ingredient: an electride state in which interstitial anionic electrons organize into a two-dimensional kagome topology embedded in the ionic lattice. Li<sub>5</sub>C has been proposed as a kagome-electride superconductor in the pressure range 50 GPa 210 GPa, reaching a maximum transition temperature of <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(T_{\mathrm c}= {48.3}~\text {K}\)</EquationSource> </InlineEquation> at 210 GPa, whereas pure Hf develops electride character in the 40 GPa 60 GPa regime of the high-pressure <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\omega \)</EquationSource> </InlineEquation> phase. Motivated by these developments, we first revisit Li<sub>5</sub>C and emphasize the importance of the electride state for its superconducting response. We then identify analogous kagome-electride features in <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\omega \)</EquationSource> </InlineEquation>-Hf and analyze their role in the superconductivity of compressed Hf. For <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\omega \)</EquationSource> </InlineEquation>-Hf, we show that spin–orbit coupling (SOC), which is significant in this <i>d</i>-band transition metal, acts in concert with electride-derived states near the Fermi level to enhance the electron–phonon coupling. This interplay provides a consistent microscopic picture of the superconducting phase and yields transition temperatures in very good agreement with previously reported experimental data.</p>

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Kagome Electride Superconductors Under Extreme Conditions

  • E. Z. da Silva,
  • Zenner S. Pereira,
  • L. Cabral

摘要

We investigate pressure-induced superconductivity in the electride compound Li5C and in elemental \(\omega \) -Hf using density functional theory (DFT) combined with Migdal–Eliashberg theory. Despite their distinct chemistry, both systems become superconducting under compression and share a key ingredient: an electride state in which interstitial anionic electrons organize into a two-dimensional kagome topology embedded in the ionic lattice. Li5C has been proposed as a kagome-electride superconductor in the pressure range 50 GPa 210 GPa, reaching a maximum transition temperature of \(T_{\mathrm c}= {48.3}~\text {K}\) at 210 GPa, whereas pure Hf develops electride character in the 40 GPa 60 GPa regime of the high-pressure \(\omega \) phase. Motivated by these developments, we first revisit Li5C and emphasize the importance of the electride state for its superconducting response. We then identify analogous kagome-electride features in \(\omega \) -Hf and analyze their role in the superconductivity of compressed Hf. For \(\omega \) -Hf, we show that spin–orbit coupling (SOC), which is significant in this d-band transition metal, acts in concert with electride-derived states near the Fermi level to enhance the electron–phonon coupling. This interplay provides a consistent microscopic picture of the superconducting phase and yields transition temperatures in very good agreement with previously reported experimental data.