手性多重半金属BeAu中的线性与非线性光学响应：量子几何视角
Linear and nonlinear optical responses in the chiral multifold semimetal BeAu: A quantum-geometric perspective
AI总结：
本研究通过全相对论第一性原理计算，从量子几何视角探究手性多重半金属BeAu的线性与非线性光学响应，揭示其响应受量子几何与多重带拓扑调控，确定其为光电现象的有前景平台。
AI中文摘要：
手性拓扑半金属为探究多重带拓扑与量子几何如何在光学及光伏响应中体现提供了天然平台。BeAu是一种手性多重半金属，在Γ、M、R点处具有带交叉，对应的陈数分别为CΓ=-4、CM=-2、CR=+4。本研究采用全相对论第一性原理计算，探究BeAu的线性光导率与二阶直流光电流响应。计算得到的带间线性光导率Re σxx(ω)可通过(e²/ℏ)ωgxx(ω)定量重现，表明其光谱特征由光子能量因子及光子能量分辨的量子度量权重变化所决定。线性位移电流电导率与辛联络密切相关，而圆注入电流 susceptibility则由Berry曲率与带间群速度差的跃迁分辨乘积所决定。在费米能级处，线性位移电流电导率在光子能量为0.05 eV时达到约-810 μA/V²。将化学势与多重交叉对齐会显著重塑两种响应，在μ=μR时产生最大的线性位移电流电导率峰，并使圆注入电流 susceptibility的大小与符号发生显著变化。圆光电流迹线强烈依赖于光子能量与化学势，且未呈现宽的量化平台，表明存在竞争的多带跃迁。本研究结果为BeAu的线性与非线性光学响应建立了统一的量子几何描述，并确定其为受多重带拓扑与量子几何调控的光电现象的有前景平台。
英文摘要：
Chiral topological semimetals provide a natural platform for exploring how multifold band topology and quantum geometry manifest in optical and photovoltaic responses. BeAu is a chiral multifold semimetal hosting band crossings at $Γ$, $M$, and $R$ with Chern numbers $C_Γ=-4$, $C_M=-2$, and $C_R=+4$, respectively. In this work, we study the linear optical conductivity and second-order dc photocurrent responses of BeAu using fully relativistic first-principles calculations. The calculated interband linear optical conductivity, Re $σ_{xx}(ω)$, is quantitatively reproduced by $(e^2/\hbar)ωg_{xx}(ω)$, showing that its spectral features are governed by the photon energy factor and the variation of the photon energy-resolved quantum-metric spectral weight. The linear shift current conductivity is closely related to the symplectic connection, whereas the circular injection current susceptibility is governed by the transition-resolved product of Berry curvature and the interband group velocity difference. At the Fermi level, the linear shift current conductivity reaches approximately -810 $μ$A/V$^2$ at a photon energy of 0.05 eV. Aligning the chemical potential with the multifold crossings strongly reshapes both responses, producing the largest linear shift current conductivity peak for $μ=μ_R$ and pronounced changes in the magnitude and sign of the circular injection current susceptibility. The circular photogalvanic trace is strongly photon-energy and chemical-potential dependent and does not exhibit a broad quantized plateau, indicating competing multiband transitions. Our results establish a unified quantum-geometric description of the linear and nonlinear optical responses of BeAu and identify it as a promising platform for optoelectronic phenomena governed by multifold band topology and quantum geometry.
