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Pressure dependence of the superconducting transition temperature of compressed LaH_(10)

机译：压缩LaH_（10）的超导转变温度的压力依赖性

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Two recent experiments [M. Somayazulu et al. Phys. Rev. Lett. 122, 027001 (2019) and A. P. Drozdov et al., Nature (London) 569, 528 (2019)] reported the discovery of superconductivity in the fcc phase of LaH10 at a critical temperature T-c between 250 and 260 K under a pressure of about 170 GPa. However, the dependence of T-c on pressure showed different patterns, i.e., the former experiment observed a continuous increase of T-c up to similar to 275 K on further increase of pressure to 202 GPa, while the latter one observed an abrupt decrease of T-c with increasing pressure. Here, based on first-principles calculations, we reveal that for the fcc-LaH10 phase, softening of the low-frequency optical phonon modes of H atoms dramatically occurs as pressure decreases, giving rise to a significant increase of the electron-phonon coupling (EPC) constant. Meanwhile, the electronic band structure near the Fermi energy is insensitive to change with respect to pressure. These results indicate that the pressure-dependent phonon softening is unlikely associated with Fermi-surface nesting, but driven by effective screening with the electronic states near the Fermi energy. It is thus demonstrated that the strong variation of EPC with respect to pressure plays a dominant role in the decrease of T-c with increasing pressure, supporting the measurements of Drozdov et al.
机译：最近的两次实验[M. Somayazulu等。物理牧师122，027001（2019）和AP Drozdov等人，Nature（伦敦）569，528（2019）]报道了在LaH10的fcc相中，在大约250到260 K的临界温度Tc下发现超导电性的现象170 GPa。然而，Tc对压力的依赖性表现出不同的模式，即前一个实验观察到，随着压力进一步增加到202 GPa，Tc持续增加直至达到275 K，而后一个实验观察到Tc随着压力的增加而突然降低。压力。在此，基于第一性原理计算，我们发现对于fcc-LaH10相，随着压力降低，H原子的低频光学声子模态会显着软化，从而显着增加了电子-声子耦合（ EPC）常数。同时，费米能量附近的电子带结构对于压力的变化不敏感。这些结果表明，与压力有关的声子软化不太可能与费米表面嵌套有关，而是受费米能量附近电子态的有效屏蔽驱动。因此证明，随着压力的升高，EPC相对于压力的强烈变化在T-c的降低中起主要作用，这支持了Drozdov等人的测量。

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  • 来源
    《Physical review》 |2019年第6期|60502.1-60502.5|共5页
  • 作者

    Wang Chongze; Yi Seho; Cho Jun-Hyung;

  • 作者单位

    Hanyang Univ Dept Phys Res Inst Nat Sci 222 Wangsimni Ro Seoul 04763 South Korea;

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