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首页> 外文期刊>Bulletin of the American Physical Society >APS -APS March Meeting 2017 - Event - Time-resolved Optical Study of Carrier Dynamics in the Weyl Semimetal TaAs
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APS -APS March Meeting 2017 - Event - Time-resolved Optical Study of Carrier Dynamics in the Weyl Semimetal TaAs

机译：APS -APS 2017年3月会议-事件-Weyl半金属TaAs中载流子动力学的时间分辨光学研究

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Since their recent discovery in 2015, Weyl semimetals have attracted attention because they are predicted to exhibit a host of novel physical and topological properties not seen in other materials. While the electronic structure of these new materials has been confirmed using surface probe methods such as angle-resolved photoemission spectroscopy (ARPES), the fundamental carrier dynamics and temporal response of these materials cannot be discerned through DC or surface-probe measurements.Here we present an ultrafast optical study of the carrier dynamics in the broken-inversion-symmetry Weyl semimetal tantalum arsenide (TaAs). We employ reflectance two-color pump-probe measurements at photon energies 0.8 eV and 1.6 eV to measure the relaxation of photoexcited electrons in in TaAs, as a function of the lattice temperature.Our measurements reveal a fast time constant ($approx $2 ps at 10 K) which we associate with the scattering of hot electrons via optical phonons, followed by a slower relaxation rate ($approx $200 ps at 10 K) attributed to acoustic phonon emission. The temperature dependence measurements show that both relaxation processes become slower with increasing lattice temperature. We present a thermodynamic model based on thermalized Dirac quasi-particles to explain the observed reflectance pump-probe results.
机译：自2015年发现以来，Weyl半金属已引起人们的关注，因为据预测它们具有其他材料所不具备的许多新颖的物理和拓扑特性。虽然这些新材料的电子结构已通过诸如角度分辨光发射光谱（ARPES）之类的表面探针方法得到了证实，但这些材料的基本载流子动力学和时间响应无法通过DC或表面探针测量来辨别。反向反转对称的Weyl半金属砷化钽（TaAs）中载流子动力学的超快光学研究。我们采用光子能量为0.8 eV和1.6 eV的反射色双色泵浦探针测量来测量TaAs中光激发电子的弛豫，它是晶格温度的函数。我们的测量揭示了快速的时间常数（约$ 2 ps / ps 10 K）与热电子通过光学声子的散射相关，随后是声子发出声子会导致弛豫速率变慢（在10 K时约为200 ps / s）。温度依赖性测量表明，两种弛豫过程都随着晶格温度的升高而变慢。我们提出了一种基于热狄拉克准粒子的热力学模型，以解释观测到的反射泵浦探针结果。

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