Bloch wave interferometry in semiconductors and correlated insulators

非技术描述：满足社会对信息技术的未来需求，需要对制造电子产品的半导体材料和以不断增加的速度传输大量信息的光进行越来越多的控制。 量子力学告诉我们，半导体中的电子应该表现得像波。要设计下一代电子和光学器件，就需要对这些电子波有详细的了解。最近，使用强大的，建筑物大小的激光器快速加速半导体中的电荷，并在它们与其他任何东西碰撞之前将它们粉碎在一起，主要研究人员的小组已经能够观察到两种加速的电子波相互干扰，类似于两块石头扔进池塘的涟漪的相互作用。根据干涉的模式，主要研究人员的小组首次能够直接从实验数据中重建半导体中干涉电子波的数学形式。在这个项目中，研究小组利用电子波的干涉来开发一种方法，以精确测量控制半导体中电荷运动以及光的吸收和发射的重要参数。这项研究是由研究生和本科生研究人员进行的，在这个过程中，他们在半导体物理，光学方面得到了严格的培训，最重要的是，解决了以前从未解决过的难题。通过这种培训，这些研究人员将能够为工业，学术界或政府开发未来的信息技术做出贡献。这些研究人员还参与了PI的普及教育推广计划，自2005年以来，该计划为当地社区的科学之夜带来了有吸引力的，吸引人的和强大的“Questboards”，让K-12学生获得电路的实践经验。技术描述：干涉测量是测量各种波编码信息的强大工具。固体中的带电准粒子有一个类波特征，这个特征在它们的布洛赫波函数中被捕获。在2011年，主要研究者的小组报告了高阶边带产生的实验发现，其中一个半导体同时被弱近红外激光和强太赫兹激光驱动，可以在梳状光谱中发射数十个近红外边带，梳齿被太赫兹频率的整数倍分开。最近，该小组报告说，从块状砷化镓（GaAs）发射的边带的偏振可以被视为来自布洛赫波的迈克尔逊干涉仪的干涉图，并使用简单的分析模型计算。本计画利用定量布洛赫波干涉法于三个方面：（1）重建体砷化镓中电子-空穴对的有效哈密尔顿量、精确的带隙及退相过程。这将为技术关键的直接带隙半导体中更精确的电子结构测量打开大门;（2）测量由极大的价带Berry曲率引起的GaAs量子威尔斯中空穴的异常位移（横向于加速电场的方向）。这将是最清晰的反常速度的演示之一--大约70年前首次预测--并且可能使直接测量一个带的局部贝里曲率成为可能;（3）从货车德瓦耳斯反铁磁体NiPS 3开始，将布洛赫波干涉术扩展到莫特绝缘体，NiPS 3是一个有希望的候选者，因为它的激子非常明亮和窄，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical description:Meeting society’s future demands for information technology requires ever-increasing control over semiconducting materials, from which electronics are made, and light, which transmits vast quantities of information at continually-increasing speeds. Quantum mechanics tells us that electrons in semiconductors should behave like waves. A detailed understanding of these electronic waves is required to engineer the next generations of electronic and optical devices. Recently, using a powerful, building-sized laser to rapidly accelerate charges in a semiconductor and smash them back together before they can collide with anything else, the principle investigator’s group has been able to observe two kinds of accelerated electronic waves interfering with one another, analogous to the interaction of ripples from two stones thrown into a pond. From the pattern of the interference, the principle investigator’s group has been able, for the first time, to reconstruct directly from experimental data the mathematical form of interfering electronic waves in a semiconductor. In this project, the research team leverages the interference of electronic waves to develop a method to precisely measure important parameters that govern both the motion of charges in and the absorption and emission of light from semiconductors. The research is carried out by graduate and undergraduate student researchers who, in the process, get rigorous training in semiconductor physics, optics, and, most importantly, solving hard problems that have never been solved before. With this training, these researchers will be well-positioned to contribute to developing future information technologies in industry, academia, or government. These researchers also participate in the PI’s popular educational outreach program that has, since 2005, brought attractive, engaging and robust "Questboards" to local community science nights for K-12 students to get hands-on experience with electrical circuits.Technical description:Interferometry is a powerful tool for measuring information encoded in waves of all sorts. Charged quasiparticles in solids have a wavelike character that is captured in their Bloch wavefunctions. In 2011, the principle investigator’s group reported the experimental discovery of high-order sideband generation, in which a semiconductor driven simultaneously by a weak near-infrared laser and a strong THz laser can emit many dozen near-infrared sidebands in a comb-like spectrum with comb teeth separated by an integer multiple of the THz frequency. Recently, the group reported that the polarizations of sidebands emitted from bulk gallium arsenide (GaAs) can be viewed as interferograms from a Michelson-like interferometer for Bloch waves, and calculated using a simple analytical model. This project uses quantitative Bloch-wave interferometry in three ways: (1) reconstruct the effective Hamiltonian, precise band gaps, and de-phasing processes of electron-hole pairs in bulk GaAs. This will open the door to much more precise electronic structure measurements in the technologically-critical direct-gap semiconductors; (2) measure anomalous displacements (transverse to the direction of the accelerating electric field) of holes in GaAs quantum wells caused by extremely large valence band Berry curvatures. This will be among the cleanest demonstrations of anomalous velocity—first predicted nearly 70 years ago—and may enable a direct measurement of the local Berry curvature of a band; (3) extend Bloch-wave interferometry to Mott insulators, beginning with the van der Waals antiferromagnet NiPS3, a promising candidate because of its extremely bright and narrow exciton, opening a new window into the electronic structure of strongly-correlated insulators.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.