论文标题
用瞬态terahertz光谱探测的狄拉克半分cd3as2膜中的半导体光载体动力学
Semiconductor-like photocarrier dynamics in Dirac Semimetal Cd3As2 film Probed with transient Terahertz Spectroscopy
论文作者
论文摘要
拓扑三维半学CD3AS2引起了人们对新型物理学和有希望的应用在红外和THZ方案中运行的光电设备中的有希望的应用。在过去几十年中的广泛研究中，一个有趣的辩论是下划线的机制，该机制在光激发后控制非平衡载体动力学。在这项研究中，已经研究了CD3AS2膜中的温度依赖性光载体动力学，已通过时间分辨的Terahertz光谱进行研究。实验结果表明，光激发会导致THZ光电导率的突然增加，随后的放松显示了各种温度和泵浦的单个指数弛豫。在220 K时，放松时间从5 K时的4.7 PS增加到7.5 ps，而寿命几乎保持恒定约为7.5 ps，温度高于220K。使用Rothwarf-Taylor模型来适合温度依赖性的放松时间，并且获得了狭窄的能量差距，狭窄的能量差距约为35 MEV，发生在Dirac Node周围。我们的THZ光谱结果表明，CD3AS2中的光载体弛豫显示出半导体的行为，而不是石墨烯和大多数金属中的热载体散射。
The topological three-dimensional Dirac semimetal Cd3As2 has drawn great attention for the novel physics and promising applications in optoelectronic devices operating in the infrared and THz regimes. Among the extensive studies in the past decades, one intriguing debate is the underlined mechanism that governing the nonequilibrium carrier dynamics following photoexcitation. In this study, the temperature dependent photocarrier dynamics in Cd3As2 film has been investigated with time-resolved terahertz spectroscopy. The experimental results demonstrate that photoexcitation results in abrupt increase in THz photoconductivity, and the subsequent relaxation shows a single exponential relaxation for various temperatures and pump fluences. The relaxation time increase from 4.7 ps at 5 K to 7.5 ps at 220 K, while the lifetime remains almost constant of ~7.5 ps with temperature above 220 K. A Rothwarf-Taylor model was employed to fit the temperature dependent relaxation time, and a narrow energy gap of ~35 meV is obtained, which occurs around the Dirac node. Our THz spectroscopy results demonstrate that the photocarrier relaxation in Cd3As2 shows a semiconductor-like behavior, rather than hot carrier scatterings in graphene and most of metals.
