Ultrafast Terahertz Light-Matter Interactions

该研究计划融合了超快激光科学和凝聚态物理学，使用太赫兹（THz）频率光脉冲在亚皮秒时间尺度上测量和控制材料中的电子自由度。在这种低能量0.1 - 30 THz范围内的光-物质相互作用由自由和束缚电荷的运动、集体激发和在奇异状态（如超导性）中产生的低能隙主导。我们使用先进的非线性光学技术和飞秒激光源来产生相位稳定的，几个周期的太赫兹光脉冲，允许这些激发的能量和时间分辨的快照。我们使用我们的方法来帮助提供对新型太阳能电池材料的更好的理解，其中THz允许人们在光首次被吸收后，在无与伦比的亚ps时间尺度上同时定量测量光电导性，激子和晶格动力学。我们将针对新的有机金属卤化物钙钛矿材料，这些材料已经在太阳能领域掀起了风暴，其中设备的快速发展超过了对材料本身的基本理解。相关的电子材料表现出金属-绝缘体转变，这是由于电子和晶格的竞争或合作贡献造成的，几十年来一直困扰着凝聚态物理学家。太赫兹光谱对金属态非常敏感，使我们能够在亚ps时间尺度上研究这些跃迁，这些跃迁是由光脉冲甚至另一个强太赫兹场触发的。通过它们不同的动力学，每种贡献的分离是可能的，这为它们的涌现特性的起源提供了深刻的见解。将锁相太赫兹脉冲的峰值电场和磁场强度分别增加到MV/cm和特斯拉附近的水平，通过与工程光场的相互作用，实现了在子周期时间尺度上对电荷和自旋激发进行时域控制的新方法。这些极端的领域可以用来访问隐藏的自由度在凝聚态物质，我们将探索使用新开发的多维非线性太赫兹光谱仪。最后，单周期，MV/cm脉冲允许通过克服太赫兹脉冲场的半周期中的功函数从金属表面产生高能电子的超短脉冲。我们将研制一种新的时间分辨电子能量损失谱仪，利用太赫兹光场控制电子脉冲宽度、能量和动量。 该计划为6名研究生和众多本科生提供超快激光科学，THz光学，材料物理和仪器开发方面的广泛培训，并在加拿大和国外开展了充满活力的合作。培训强调批判性思维，团队合作，沟通和网络技能，支持直接受益于加拿大的创新领域的成功研究生涯。

This research program merges ultrafast laser science and condensed matter physics, using pulses of terahertz (THz) frequency light to measure and control electronic degrees of freedom in materials on sub-picosecond time scales. The light-matter interaction in this low energy 0.1 - 30 THz regime is dominated by the motion of free and bound charges, collective excitations and low energy gaps arising in exotic states such as superconductivity. We use advanced nonlinear optical techniques and femtosecond laser sources to generate phase stable, few cycle THz pulses of light that allow energy and time-resolved snapshots of these excitations. We use our methods to help provide an improved understanding of novel solar cell materials, where THz allows one to quantitatively measure photoconductivity, exciton and lattice dynamics simultaneously, on unmatched sub-ps time scales after light is first absorbed. We will target the new organometallic halide perovskite materials that have taken the solar community by storm, where the rapid development of devices outpaces the basic understanding of the materials themselves. Correlated electron materials exhibiting metal-insulator transitions resulting from competing or cooperating electronic and lattice contributions have puzzled condensed matter physicists for decades. Intrinsically sensitive to the metallic state, THz spectroscopy allows us to study these transitions on sub-ps time scales after they are triggered by an optical pulse or even another strong THz field. Separation of each contribution is then possible through their different dynamics, providing deep insight into the origin of their emergent properties. Increasing the peak electric and magnetic field strength of phase-locked THz pulses to MV/cm and near Tesla levels, respectively, enables a new method of time-domain control over charge and spin excitations on sub-cycle time scales, through interaction with engineered light fields. These extreme fields can be used to access hidden degrees of freedom in condensed matter that we will explore using a newly developed multi-dimensional nonlinear THz spectrometer. Finally, single-cycle, MV/cm pulses allow the generation of ultra-short bursts of energetic electrons from metal surfaces by overcoming the work function in the half-cycle of the THz pulse field. We will develop a new time-resolved electron energy loss spectrometer with electron pulse duration, energy and momentum controlled by THz optical fields. This program offers extensive training in ultrafast laser science, THz optics, materials physics and instrumentation development for 6 graduate students and numerous undergraduates with vibrant collaborations in Canada and abroad. Training emphasizes critical thinking, teamwork, communication and networking skills that support a successful research career in innovative areas of direct benefit to Canada.