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Electron-phonon coupling superconductivity and tunable topological state in carbon-rich selenide monolayers

Panlong KongSchool of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, ChinaXiaotao ZhangSchool of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, ChinaJingJing WangCollege of Computer and Information Engineering, Hubei Normal University, Huangshi 435002, ChinaWenhui TianCollege of Computer and Information Engineering, Hubei Normal University, Huangshi 435002, ChinaYuxiang NiSchool of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, ChinaBai SunFrontier Institute of Science and Technology (FIST), Xi'an Jiaotong University, Xi'an, Shaanxi 710049, ChinaHongyan WangSchool of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, ChinaHui WangSchool of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, ChinaYuan Ping FengDepartment of Physics and Centre for Advanced Two-Dimensional Materials, National University of Singapore, Singapore 117551, SingaporeYuanzheng ChenSchool of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, China

2023en

ABI

Annotatsiya

The coexistence of Dirac cones and Van Hove singularities (VHSs), as the notable feature on prominent electronic band structure in recently hot-topic Lieb lattice and twisted graphene superlattice materials, has recently drawn tremendous attention since it offers an ideal platform for realizing correlation-driven electronic states (e.g., superconductivity and topological state). Here, we have identified two two-dimensional (2D) crystals, namely ${\mathrm{C}}_{4}\mathrm{Se}$ and ${\mathrm{C}}_{5}\mathrm{Se}$, which exhibit the coexistence of Dirac cones and VHSs. Based on ab initio calculations and the Bardeen-Cooper-Schrieffer theory, we investigated the electron-phonon coupling and possible superconductivity in both structures. The results indicate that ${\mathrm{C}}_{4}\mathrm{Se}$ possesses intrinsic superconducting states, whereas ${\mathrm{C}}_{5}\mathrm{Se}$ exhibits tunable superconductivity when doped. Their superconducting critical temperature (${T}_{c}$) can reach up to 11.6 and 11.2 K, respectively, surpassing the majority of 2D superconductors. Besides, we uncovered an approximate Dirac cone in ${\mathrm{C}}_{6}\mathrm{Se}$ with a small band gap of 0.17 eV. Via the application of a biaxial compressive strain, remarkably, the ${\mathrm{C}}_{6}\mathrm{Se}$ can be transformed into a topological insulator. These findings highlight the potential of carbon-rich C-Se 2D crystals as a promising platform for investigating fascinating band structures and physical states, thus advancing our comprehension of 2D crystals.

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Identifikatorlar

DOI: 10.1103/physrevb.107.184115

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