Role of surface functional groups to superconductivity in Nb$_2$C-MXene: Experiments and density functional theory calculations

Kai Wang; Haolin Jin; Hongye Li; Zhongquan Mao; Lingyun Tang; Dan Huang; Ji-Hai Liao; Jiang Zhang

doi:10.1016/j.surfin.2021.101711

paper

Role of surface functional groups to superconductivity in Nb $_{2}$ C-MXene: Experiments and density functional theory calculations

arXiv:2201.00298 · doi:10.1016/j.surfin.2021.101711

Abstract

The recently discovered surface-group-dependent superconductivity in Nb $_{2}$ C-MXene fabricated by the molten salts method is attracting wide attention. However, regarding the superconductivity of Nb $_{2}$ C-MXene with functional F groups (Nb $_{2}$ CF $_{x}$ ), there were some conflicting results in experimental and theoretical studies. Herein, we systematically carried out experimental and theoretical investigations on the superconductivity in Nb $_{2}$ C-MXene with the Cl functional group (Nb $_{2}$ CCl $_{x}$ ) and Nb $_{2}$ CF $_{x}$ . The experimental results of the Meissner effect and zero resistivity have proved that Nb $_{2}$ CClx is superconducting with the transition temperature (Tc) ~ 5.2 K. We extract its superconducting parameters from the temperature dependence of resistivity and the field dependence of the magnetization. The Ginzburg-Landau parameter K $_{G}$ $_{L}$ is estimated to be 2.41, indicating that Nb $_{2}$ CClx is a typical type-II superconductor. Conversely, both magnetic and electrical transport measurements demonstrate that Nb $_{2}$ CF $_{x}$ is not superconducting. The first-principles density functional theory (DFT) calculations show that the Tc of Nb $_{2}$ Cl $_{x}$ is ~ 5.2 K, while Nb $_{2}$ CF $_{x}$ is dynamically unstable with imaginary frequency in phonon spectrum, which is in good agreement with the experimental results. Our studies not only are useful for clarifying the present inconsistency but also offer referential significance for future investigations on the superconductivity of MXenes.

arXiv commentAccepted by Surfaces and Interfaces,30 pages, 7 figures

Role of surface functional groups to superconductivity in Nb $_{2}$ C-MXene: Experiments and density functional theory calculations

Abstract

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Role of surface functional groups to superconductivity in Nb2​C-MXene: Experiments and density functional theory calculations

Abstract

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Role of surface functional groups to superconductivity in Nb $_{2}$ C-MXene: Experiments and density functional theory calculations