方向依赖的磁电导率：来自偶极拓扑半金属

中文摘要 AI 辅助

我们在弛豫时间近似下，利用半经典玻尔兹曼形式计算了两带涡旋节线环（VNR）半金属和三带霍普夫半金属（HSM）的线性磁电导率。我们考虑了三种不等价的平面霍尔构型，其中电场（$\boldsymbol E$）和磁场（$\boldsymbol B$）相对于节线环平面和贝里曲率（BC）偶极轴的方向不同。与韦尔半金属和多折叠半金属中贝里曲率通量源于类单极源不同，这两种系统都拥有类偶极的BC源和消失的陈数。我们一致地计算到磁场的三次方阶，评估了电导率中的德鲁德、BC、轨道磁矩（OMM）、反常霍尔和洛伦兹力贡献。在这两种系统中，偶极BC和OMM在面内响应通道中产生$|\boldsymbol B|$的奇次幂，而这些通道在具有类单极BC源的系统中是对称性禁止的。对于HSM，带间散射对电导率的贡献恒为零。通过将VNR与$\mathcal{PT}$破缺的有隙节线环以及将HSM与赝自旋-1三重点半金属进行比较，我们证明了BC的偶极性质产生了磁电响应中的独特特征，而这些特征在具有类单极BC通量的半金属中是不存在的。

英文摘要

We compute the linear magnetoelectric conductivity of a two-band vortex nodal-ring (VNR) semimetal and a three-band Hopf semimetal (HSM) within the semiclassical Boltzmann formalism in the relaxation-time approximation. We consider three inequivalent planar-Hall configurations, in which the electric ($\boldsymbol E$) and magnetic ($\boldsymbol B$) fields are oriented differently with respect to the nodal-ring plane and the BC-dipole axis. Unlike Weyl and multifold semimetals, where Berry-curvature (BC) flux originates from monopole-like sources, both systems host dipole-like BC sources and vanishing Chern numbers. Working consistently to cubic order in the magnetic field, we evaluate the Drude, BC, orbital-magnetic-moment (OMM), anomalous-Hall, and Lorentz-force contributions to the conductivity. In both systems, the dipolar BC and OMM generate odd powers of $|\boldsymbol B|$ in in-plane response channels that are symmetry-forbidden in systems with monopole-like BC sources. For the HSM, the internode-scattering contribution to the conductivity vanishes identically. By comparing the VNR with a $\mathcal{PT}$-broken gapped nodal ring and the HSM with a pseudospin-1 triple-point semimetal, we demonstrate that the dipolar nature of the BC gives rise to distinctive features in magnetoelectric response that are absent in semimetals with monopole-like BC flux.

发表机构

• Shiv Nadar Institution of Eminence（希夫纳达尔卓越机构）

机构由 AI 辅助整理，请以论文原文为准。

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55 pages, 9 figures