发表机构
Indian Institute of Science Education and Research (IISER) Tirupati（印度科学教育研究所提鲁帕蒂分校）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究对偶极-八极烧绿石磁体中的费米子$Z_2$自旋液体进行射影对称群分类，发现其平均场通道与有效自旋-1/2及玻色子情形不同，并通过自洽能量最小化得到相图，计算自旋子谱与比热，为无间隙分数化热力学提供费米子解释。
AI 中文摘要
我们在偶极-八极（DO）烧绿石晶格上构造并分类了费米子部分子（parton）的$Z_2$量子自旋液体（QSLs）。DO赝自旋与有效自旋-1/2 Kramers双重态共享空间群和时间反演代数，其射影对称群（PSG）产生与一般费米子分类相同的48个对称$Z_2$类。我们证明，由一组与子格无关的算子编码的独特DO对称作用，选择了物理上不同的对称允许的平均场通道集合，因此所得的ansatze、自旋子谱和可观测量与有效自旋-1/2情形及玻色子DO分类均不同。将各向异性XYZ交换模型分解为所有对称的单态和三重态跳跃及配对通道，并自洽地最小化平均场能量，我们得到了($\ ilde{J_x}, \ ilde{J_z}$)平面上的相图，其中只有少数$Z_2$态被稳定，其中一些支持无间隙或平带自旋子谱。对于这些态，我们计算了自旋子能带结构、低温比热和动力学自旋结构因子，并论证了幂律比热指数是自旋子节点结构的诊断指标。近线性温度依赖的比热以及结构因子中的宽连续谱，为DO材料（如$Nd_2ScNbO_7$）中报道的无间隙、分数化热力学提供了费米子部分子解释，补充了基于Ce的化合物的玻色子量子自旋冰图像。这项工作将DO烧绿石QSL的费米子部分子分类扩展到$U(1)$扇区之外，其中$Z_2$拓扑序由费米子和玻色子自旋子同样自然地实现。
英文摘要
We construct and classify $Z_2$ quantum spin liquids (QSLs) of fermionic partons on the dipolar-octupolar (DO) pyrochlore lattice. The DO pseudospin shares the space-group and time-reversal algebra of the effective spin-1/2 Kramers doublet, its projective symmetry group (PSG) yields the same 48 symmetric $Z_2$ classes as the generic fermionic classification. We show, the distinct DO symmetry action, encoded in a set of sublattice-independent operators, selects a physically different set of symmetry-allowed mean-field channels, so that the resulting ansatze, spinon spectra, and observables differ from both the effective spin-1/2 case and the bosonic DO classification. Decomposing the anisotropic XYZ exchange model into all symmetric singlet and triplet hopping and pairing channels and minimizing the mean-field energy self-consistently, we obtain phase diagrams in the ($\tilde{J_x}, \tilde{J_z}$) plane in which only a few $Z_2$ states, several supporting gapless or flat-band spinon spectra, are stabilized. For these states we compute the spinon band structures, the low-temperature specific heat, and the dynamical spin structure factor, and we argue that the power-law specific-heat exponent is a diagnostic of the spinon nodal structure. A near-linear-in-temperature specific heat together with broad continua in the structure factor gives a fermionic-parton account of the gapless, fractionalized thermodynamics reported in DO materials such as $Nd_2ScNbO_7$, complementing the bosonic quantum-spin-ice picture of the Ce-based compounds. The work extends the fermionic-parton classification of DO pyrochlore QSLs beyond the $U(1)$ sector, where $Z_2$ topological order is realized equally naturally by fermionic and bosonic spinons.
Comments24 pages, 11 figures
