无序诱导的Weyl半金属中非线性霍尔效应的调制

中文摘要 AI 辅助

我们在半经典玻尔兹曼方法框架下研究了杂质散射对Weyl半金属非线性霍尔响应的影响。我们推导了针对一般动量依赖的输运弛豫时间的整流和二次谐波电导率张量，并微观上评估了短程、高斯、屏蔽库仑和磁性杂质情况下的该量。对于标量无序，弛豫时间是各向同性且与手性无关的。非线性霍尔响应随后由与贝里曲率相关的反常速度决定，且有限的净响应要求能量上不等价的Weyl节点以避免相反手性之间的抵消。极化磁性杂质导致定性不同的行为。我们发现一阶和二阶玻恩振幅之间的干涉产生了依赖于螺旋度的各向异性弛豫时间修正。这种各向异性改变了非线性霍尔电导率的张量结构，并在电场相对于杂质极化的适当取向下产生有限的二次谐波电流。然而，对于代表性参数，各向异性贡献比主导的各向同性响应小几个数量级。这些结果确立了杂质散射的微观形式如何通过输运弛豫时间进入Weyl半金属的非线性霍尔响应。

英文摘要

We study the effects of impurity scattering on the nonlinear Hall response of Weyl semimetals within the semiclassical Boltzmann approach. We derive the rectified and second-harmonic conductivity tensors for a general momentum-dependent transport relaxation time and evaluate this quantity microscopically for short-range, Gaussian, screened Coulomb, and magnetic impurities. For scalar disorder, the relaxation time is isotropic and chirality independent. The nonlinear Hall response is then determined by the anomalous velocity associated with the Berry curvature, and a finite net response requires energetically inequivalent Weyl nodes to avoid cancellation between opposite chiralities. Polarized magnetic impurities lead to a qualitatively different behavior. We find that interference between the first- and second-order Born amplitudes generates a helicity-dependent anisotropic correction to the relaxation time. This anisotropy changes the tensor structure of the nonlinear Hall conductivity and gives rise to a finite second-harmonic current for suitable orientations of the electric field relative to the impurity polarization. For representative parameters, however, the anisotropic contribution is several orders of magnitude smaller than the dominant isotropic response. These results establish how the microscopic form of impurity scattering enters the nonlinear Hall response of Weyl semimetals through the transport relaxation time.

发表机构

• Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México（墨西哥国立自治大学核科学研究所）

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10 pages, 2 figures