太赫兹辐射驱动的CdHgTe晶体中Kane费米子的磁光电galvanic效应
Magnetophotogalvanic Effects Driven by Terahertz Radiation in CdHgTe Crystals with Kane Fermions
AI总结：
研究太赫兹辐射诱导的磁光电效应在CdHgTe晶体中的表现，通过Kane模型解释共振现象，揭示费米子能谱对电荷电流的影响。
摘要：
我们报道了在含Kane费米子的CdHgTe晶体中观察到的太赫兹辐射诱导的磁光电效应（MPGE）的全面研究。在Cd$_{x}$Hg$_{1-x}$Te薄膜（x=0.15和0.22）中，通过平面磁场检测到MPGE。在液氦温度下，磁场变化导致MPGE电流出现多个共振。在x=0.22的非倒置能带结构中，共振由回旋共振和杂质能级的光电离引起。在x=0.15的倒置能带结构中，共振源于回旋共振和能带间光跃迁。Kane模型计算的能带结构完美描述了所有共振位置。特别是，由太赫兹辐射激发的能带间跃迁引起的共振MPGE，是Kane费米子在特定Cd含量和温度范围内的无能隙能谱所致。此外，除了共振MPGE电流外，还检测到由间接光学跃迁（Drude-like）引起的非共振电流。该贡献具有非单调的磁场依赖性，低磁场下线性增加，中等磁场处达到最大值，高磁场下减少。非共振MPGE随温度升高急剧下降，但在室温下仍可测量。所发展的理论表明，MPGE电流源于散射概率中的立方动量依赖的自旋相关项。这些效应的不对称性导致纯自旋电流，由于塞曼效应转化为电荷电流。
英文摘要：
We report on the observation and comprehensive study of the terahertz radiation induced magneto-photogalvanic effect (MPGE) in bulk CdHgTe crystals hosting Kane fermions. The MPGE has been detected in Cd$_{x}$Hg$_{1-x}$Te films with Cd contents $x = 0.15$ and $0.22$ subjected to an in-plane magnetic field. At liquid helium temperature we observed multiple resonances in MPGE current upon variation of magnetic field. In the $x = 0.22$ with noninverted band structure, the resonances are caused by cyclotron resonance (CR) and photoionization of an impurity level. In the $x = 0.15$ films with an inverted band structure, they originate from the CR and interband optical transitions. Band structure calculated by the Kane model perfectly describes positions of all resonances. In particularly, the resonant MPGE caused by interband transitions excited by THz radiation is caused by the gapless energy spectrum of Kane fermions realized in materials with certain Cd contents and temperature range. In addition to the resonant MPGE current we detected a nonresonant one due to indirect optical transitions (Drude-like). This contribution has a nonmonotonic magnetic field dependence increasing linearly at low magnetic field $B$, approaching a maximum at moderate field and decreasing at high $B$. While the nonresonant MPGE decreases drastically with increasing temperature, it is well measurable up to room temperature. The developed theory demonstrates that the MPGE current arises due to cubic in momentum spin-dependent terms in the scattering probability. The asymmetry caused by these effects results in a pure spin current which is converted into an electric current due to the Zeeman effect.
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