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arXiv 2401.03348cond-mat.supr-con
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通过表面氟化增强单层NbSe$_2$中的Ising超导性

Enhancement of Ising superconductivity in monolayer NbSe$_2$ via surface fluorination

Jizheng Wu, Wujun Shi, Chong Wang, Wenhui Duan, Yong Xu, Chen Si

AI总结:

基于Migdal-Eliashberg理论和BdG哈密顿量,证明表面氟化可通过维持镜面对称、抑制电荷密度波及增强电声子耦合,显著提升单层NbSe$_2$的Ising超导转变温度和上临界场。

摘要:

最近发现的Ising超导体因其反常大的面内上临界场($B_{c2}$)而引起了广泛关注。然而,Ising配对机制中所需的强自旋轨道耦合通常使这些超导体以重元素为主,且超导转变温度($T_c$)显著偏低。在此,基于Migdal-Eliashberg理论和平均场Bogoliubov-de Gennes哈密顿量,我们证明了通过表面氟化可显著增强单层NbSe$_2$中的Ising超导性,$T_c$和$B_{c2}$的同时提高证实了这一点。这种增强源于三个主要因素。首先,氟原子对称且稳定地附着在单层NbSe$_2$的两侧,从而维持了面外镜面对称性,并将载流子自旋锁定在面外。其次,氟化抑制了单层NbSe$_2$中的电荷密度波,并在费米能级附近诱导出van Hove奇点,导致载流子数量显著增加,从而增强了电声子耦合(EPC)。最后,与氟相关的低频声子模式的出现进一步增强了EPC。我们的研究结果提出了一条在不损害Ising配对的前提下提高二维Ising超导体$T_c$的有前途的途径。

英文摘要:

Recently discovered Ising superconductors have garnered considerable interest due to their anomalously large in-plane upper critical fields ($B_{c2}$). However, the requisite strong spin-orbital coupling in the Ising pairing mechanism generally renders these superconductors heavy-element dominant with notably low superconducting transition temperatures ($T_c$). Here, based on the Migdal-Eliashberg theory and the mean-field Bogoliubov-de Gennes Hamiltonian, we demonstrate a significant enhancement of Ising superconductivity in monolayer NbSe$_2$ through surface fluorination, as evidenced by concomitant improvements in $T_c$ and $B_{c2}$. This enhancement arises from three predominant factors. Firstly, fluorine atoms symmetrically and stably adhere to both sides of the monolayer NbSe$_2$, thereby maintaining the out-of-plane mirror symmetry and locking carrier spins out-of-plane. Secondly, fluorination suppresses the charge density wave in monolayer NbSe$_2$ and induces a van Hove singularity in the vicinity of the Fermi level, leading to a marked increase in the number of carriers and, consequently, strengthening the electron-phonon coupling (EPC). Lastly, the appearance of fluorine-related, low-frequency phonon modes further augments the EPC. Our findings suggest a promising avenue to elevate $T_c$ in two-dimensional Ising superconductors without compromising their Ising pairing.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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