AI 中文总结
研究以H$_3$Se为参考，结合第一性原理计算与随机自洽谐波近似，研究D$_3$Se在60 - 200 GPa的振动和超导特性，发现非谐效应使声子谱重整化、晶格稳定，改变电子 - 声子耦合致超导临界温度降低，还揭示其对同位素效应的控制作用。
AI 中文摘要
富氢超导体在高压H$_3$S中发现高温超导后备受关注，这为高压下室温超导带来了新希望。本文以H$_3$Se为参考体系，通过第一性原理计算与随机自洽谐波近似相结合的方法，研究了D$_3$Se在Im\bar{3}m相60 - 200 GPa范围内的振动和超导特性。这些效应使声子谱发生显著重整化，并使晶格稳定至至少70 GPa，远低于谐波预测的>110 GPa。最终，声子重整化改变了电子 - 声子耦合，使超导临界温度在研究压力范围内相对于标准计算降低了约3 - 16 K。在Migdal - Eliashberg理论中考虑非谐声子，在75 GPa时得到$T_c \approx 154$ K 。研究非谐性在同位素效应中的作用发现，在200 GPa时它将同位素系数$\alpha$抑制至0.29，比谐波值（0.44）低三分之一，接近BCS极限0.5。这种显著降低表明非谐性从根本上控制了该体系的同位素效应。非谐与谐波描述之间的明显差异凸显了针对性实验工作的必要性，以解决压缩氢化物中持续存在的理论 - 实验差异的根源。
英文摘要
Hydrogen-rich superconductors have garnered considerable interest following the discovery of hot superconductivity in high pressure H$_3$S, reviving prospects for room temperature superconductors under high-pressures. Using H$_3$Se as a reference system, we investigate the vibrational and superconducting properties of D$_3$Se in the Im\bar{3}m phase across 60-200 GPa by combining first-principles calculations with the stochastic self-consistent harmonic approximation to treat ionic quantum and anharmonic effects. These effects introduce significant renormalization to the phonon spectra and stabilize the lattice down to at least 70 GPa, well below the harmonic prediction of >110 GPa. Ultimately, the phonon renormalizations alter the electron-phonon coupling, introducing a decrease in the superconducting critical temperature by about 3-16 K across the studied pressure range with respect to standard calculations. Including anharmonic phonons within the Migdal-Eliashberg theory yields $T_c \approx 154$ K at 75 GPa (with $μ^* = 0.1$, $λ = 3.0$), highlighting D3Se as a promising high-Tc superconductor at moderate pressures. Examining the role of anharmonicity in the isotope effect, we find that at 200 GPa it suppresses the isotope coefficient $α$ to 0.29 one third below the harmonic value (0.44) which approaches the BCS limit of 0.5. This dramatic reduction demonstrates that anharmonicity fundamentally governs the isotope effect on this system. The stark discrepancy between anharmonic and harmonic descriptions underscores the need for targeted experimental efforts to resolve the origin of the persistent theory-experiment discrepancy in compressed hydrides.
