CAREER:Cyclotron resonance spectroscopy of interacting fermions

非技术摘要：电子在材料中移动的方式决定了任何系统的许多基本特性，例如导电性或反射率。然而，在大多数材料中，无论我们考虑孤立的一个电子，还是多个电子一起运动，这些性质都是定性相同的。如果电子相互作用，会产生更微妙和有趣的效应，在这种情况下，出现的行为不可能只存在于一个或几个电子中：一个简单的类比是，海浪是大量水分子的相干运动。然而，将相互作用的电子的微观行为与材料的整体行为联系起来通常是具有挑战性的。在这项工作中，首席研究员使用红外光照射通过薄材料的测量来探测在几个有趣的情况下相互作用的电子系统的行为。其中包括超净石墨烯设备，由单原子厚的碳原子片组成，其中电子相互作用产生迷人的多粒子量子态。这些设备也被放置在小腔体中，以极大地放大红外光的强度;在这些条件下，电子和光波被认为合并成新的量子态，忘记了它们作为独立实体的起源。最后，在某些材料中，电子相互作用如此强烈，以至于没有一个可以独立移动;然而，它们可以以相关的方式自由旋转，产生迷人的流体般的行为。这种物理现象非常难以分离和探测，但最近的理论工作表明，红外光可以辨别这种流体状状态是否存在。此外，主要研究者导致多样性举措物理系内，导致拉丁美洲/研究生的增加。这些努力与大学和美国物理学会的桥梁项目相结合，使物理学界的面孔更能代表整个国家。 技术摘要：许多相互作用的粒子系统既迷人又神秘，表现出宏观相关的行为，往往是知之甚少。在这个项目中，主要研究人员使用红外磁谱法探索相关电子物理学，当应用于具有线性能带结构或非抛物线色散的材料时，该方法对多粒子相互作用具有新颖的灵敏度。这种线性系统曾经非常罕见，但现在出现在大量现代量子材料中。主要研究人员利用专用的红外磁光谱能力，在高达14 T的磁场和接近100 mK的温度下研究石墨烯和强相关材料，光学器件能够处理原子级薄材料的微观样品。升级将进一步提高信噪比、分辨率和光谱范围。这使得三个不同但相互关联的项目的探索：第一，在石墨烯的整数和分数量子霍尔制度的电子-电子相互作用效应的光谱学，以阐明它们在对称性破缺和多粒子基态形成中的作用。在第二个项目中，这些石墨烯器件被放置在具有红外共振的镜面腔中，以增强光与石墨烯中回旋共振跃迁的相互作用。据预测，这将实现腔量子电动力学的超强耦合机制，使石墨烯成为光和物质强相互作用系统的最前沿。此外，石墨烯朗道能级的不均匀间隔意味着可以实现适当的两能级系统，预示着一种在红外线中工作并原生于高磁场的新型石墨烯基量子比特。在第三个项目中，研究了强相关绝缘体，包括SmB 6，YbB 12，1 T-TaSe 2和1 T-TaS 2。这些材料被认为拥有一个不寻常的中性自旋费米表面，特别是预计将表现出新颖的回旋共振模式。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Non-technical Abstract:The way in which electrons move through materials determines many of the fundamental properties of any system, such as conductivity or reflectivity. In most materials, however, these properties are qualitatively the same whether we consider one electron in isolation, or many moving in concert. More subtle and interesting effects can arise if the electrons interact with one another, in which case emergent behaviors appear that cannot exist for just one or a few electrons: a simple analogy is that ocean waves are the coherent motion of vast numbers of water molecules. Yet connecting the microscopic behavior of interacting electrons to the overall behavior of a material is often challenging. In this work, the principal investigator uses measurements of infrared light shining through thin materials to probe the behavior of interacting electron systems in several interesting cases. These include ultra-clean graphene devices, comprised of single-atom-thick sheets of carbon atoms in which the electrons interact to generate fascinating many-particle quantum states. These devices are also placed in small cavities to greatly amplify the intensity of the infrared light; under these conditions the electrons and waves of light are thought to merge into novel quantum states that forget their origins as separate entities. Finally, in some materials the electrons interact so strongly that none can independently move; yet they are free to rotate in a correlated fashion to yield fascinating, fluid-like behaviors. This physics is exceedingly difficult to isolate and probe, but recent theoretical work suggests that infrared light can discern whether such a fluid-like state is present. In addition, the principle investigator leads diversity initiatives within the Physics Department that are leading to an increase in Latino/a graduate students. These efforts are being coupled to bridge programs operated in the university at large and also by the American Physical Society, toward making the faces in the physics community more representative of the nation as a whole. Technical Abstract:Systems of many interacting particles are both fascinating and enigmatic, exhibiting macroscopic correlated behaviors that are often poorly understood. In this project the principle investigator explores correlated electron physics using infrared magnetospectroscopy, which acquires a novel sensitivity to many-particle interactions when applied to materials that have a linear band structure or non-parabolic dispersion. Such linear systems were once incredibly rare but now arise in multitudes of modern quantum materials. The principle investigator utilizes a dedicated infrared magneto-spectroscopy capability to study graphene and strongly correlated materials in fields up to 14 T and temperatures approaching 100 mK, with optics capable of working with microscopic samples of atomically-thin materials. Upgrades will further enhance signal-to-noise, resolution, and spectral range. This enables explorations of three distinct but inter-related projects: first, spectroscopy of electron-electron interaction effects in the integer and fractional quantum Hall regimes in graphene, toward elucidating their role in symmetry breaking and formation of many-particle ground states. In the second project, these graphene devices are placed in mirrored cavities having a resonance in the infrared to enhance the interaction of light with the cyclotron resonance transitions in graphene. This is predicted to achieve the ultrastrong coupling regime of cavity quantum electrodynamics, vaulting graphene to the forefront of systems hosting strongly interacting light and matter. Moreover, the uneven spacing of graphene Landau levels implies a proper two-level system is achievable, presaging a novel graphene-based qubit operating in the infrared and native to high magnetic fields. In the third project, strongly correlated insulators including SmB6, YbB12, 1T-TaSe2 and 1T-TaS2 are explored. These materials are thought to host an unusual Fermi surface of neutral spinons, specifically predicted to exhibit novel cyclotron resonance modes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.