Topological Enhancement of Nonlinear Transports in Unconventional Point-Node Semimetals
PHYSICAL REVIEW B(2023)
摘要
The topological singularity of the Bloch states close to the Fermi level significantly enhances nonlinear electric responses in topological semimetals. Here, we systematically characterize this enhancement for a large class of topological nodal-point fermions, including those with linear, linear-quadratic, and quadratic dispersions. Specifically, we determine the leading power-law dependence of the nonlinear response functions on the chemical potential $\mu$ defined relative to the nodal point. We identify two characteristics that qualitatively improve nonlinear transports compared to those of conventional Dirac and Weyl fermions. First, the type II (over-tilted) spectrum leads to the $\log\mu$ enhancement of nonlinear response functions having zero scaling dimension with respect to $\mu$, which is not seen in a type-I (moderately or not tilted) spectrum. Second, the anisotropic linear-quadratic dispersion increases the power of small-$\mu$ divergence for the nonlinear response tensors along the linearly dispersing direction. Our work reveals new experimental signatures of unconventional nodal points in topological semimetals as well as provides a guiding principle for giant nonlinear electric responses.
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关键词
nonlinear transport,topological enhancement,point-node
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