CAREER:Cyclotron resonance spectroscopy of interacting fermions

点击翻译按钮获取中文摘要

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.