AI 中文总结
本研究用混合维周期安德森模型结合BCS-RPA，分析UTe₂的磁激发，发现仅B₂ᵤ超导态会在Q_Y处产生超导诱导自旋共振，确立了适用于三维重费米子多带超导体的符号改变准则。
AI 中文摘要
我们采用混合维周期安德森模型研究UTe₂的动力学自旋响应。在BCS-RPA形式框架内，我们探究准粒子的f轨道特征如何影响正常态和超导（SC）态下的磁激发。正常态中，局域f电子与传导电子间的有限杂化会产生杂化能隙，并增强Q_Y=(0,π,0)处的自旋响应，表明该磁激发源于跨杂化能隙的粒子-空穴散射。超导态中，我们对比自旋三重态序参量的四种奇宇称不可约表示A_u、B_{1u}、B_{2u}、B_{3u}，发现对于自旋磁化率平行于d矢量的分量，仅在B_{2u}态中会在Q_Y处出现显著的超导诱导自旋共振。该行为源于B_{2u}序参量在k_z=π附近由Q_Y连接的、受f电子主导的费米面相关区域间保持有限并改变符号。符号改变准则适用于三维重费米子体系的多带超导体，需满足三个条件：（i）由嵌套矢量连接的费米面的低维部分；（ii）f电子特征占主导；（iii）该部分存在有限的SC能隙振幅。
英文摘要
We study the dynamical spin response of UTe$_2$ by using a mixed-dimensional periodic Anderson model. Within the BCS-RPA formalism, we examine how the $f$-orbital character of the quasiparticles affects magnetic excitations in both the normal and superconducting (SC) states. In the normal state, finite mixing between localized $f$ electrons and conduction electrons produces a hybridization gap and enhances the spin response at $\mathbf{Q}_{\mathrm{Y}} = (0,π,0)$, indicating that the magnetic excitation originates from particle--hole scattering across the hybridization gap. In the SC state, we compare four odd-parity irreducible representations, $A_u$, $B_{1u}$, $B_{2u}$, and $B_{3u}$, for the spin-triplet order parameter. We find that, for the component of the spin susceptibility parallel to the $\mathbf{d}$ vector, a pronounced superconductivity-induced spin resonance appears at $\mathbf{Q}_{\mathrm{Y}}$ only in the $B_{2u}$ state. This behavior arises because the $B_{2u}$ order parameter remains finite and changes its sign between the relevant $f$-electron-dominated Fermi-surface regions connected by $\mathbf{Q}_\mathrm{Y}$ near $k_z=π$. The sign-change criterion is applicable to multiband superconductors in three-dimensional heavy-fermion systems, in the presence of (i) low-dimensional portions of the Fermi surface connected by a nesting vector, (ii) the dominance of the $f$-electron character, and (iii) the finite amplitude of SC gap on the portions.
Comments16 pages, 13 figures, and 2 tables
