Abstract
Boron-rich lithium borocarbides are promising candidates for phonon-mediated high-temperature superconductors due to their metallic σ-bonding electrons. Here, we use the cluster expansion method to identify energetically stable configurations (colorings) of Li2B3C and Li3B4C2, which are characterized by a distinctive pattern of alternating B-B and B-C zigzag chains. Surprisingly, the optimal configuration of Li2B3C exhibits an extremely low superconducting transition temperature of Tc < 0.03 K, which is attributed to the suppression of deformation potentials near the Fermi level caused by the specific electron filling of B-B zigzag chains. However, the σ-bonding electrons at the Fermi level are highly sensitive to external strain or pressure. Specifically, applying a −5% compressive uniaxial strain can significantly enhance the electron-phonon coupling and the Eliashberg spectral function, boosting up Tc to 37 K. This work not only presents a strategy for achieving high critical temperatures in LinBn+1Cn+1 compounds, but also provides valuable insights into the complex interplay between electronic structure and superconducting interaction.
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Data availability
The data that support the findings of this study are available from the corresponding author upon reasonable request.
Code availability
The calculations were performed using the proprietary code VASP62, the open-source code ATAT65, the open-source code Wannier9067, the open-source code Quantum ESPRESSO69, and the open-source code EPW42. Wannier90 and EPW are freely released under the GNU General Public License (v2). ATAT and Quantum ESPRESSO are freely released under the Creative Commons Attribution 4.0 International License.
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Acknowledgements
We thank Xi Xu and Yue-chao Wang for useful discussions. The work is supported by the National Natural Science Foundation of China (Grant No: 22273002, 12404153) and the Fundamental Research Fund for the Central Universities (Grant No: FRF-TP-25-040). The calculations were done on Hefei advanced computing center, etc.
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Jiangping Hu, Hong Jiang and Yuhao Gu designed the project. Yuhao Gu performed the first-principles calculations. Yuhao Gu, Tao Xiang and Hong Jiang wrote the manuscript. All authors participated in discussions and provided comments on the manuscript.
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Gu, Y., Hu, J., Jiang, H. et al. Optimal coloring and strain-enhanced superconductivity in LinBn+1Cn−1. Commun Phys (2026). https://doi.org/10.1038/s42005-026-02495-w
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DOI: https://doi.org/10.1038/s42005-026-02495-w
