Bloch wave interferometry in semiconductors and correlated insulators

非技术描述：满足社会未来对信息技术的需求，要求对半导体材料和光的控制不断增加，半导体材料是电子产品的原料，光以不断增加的速度传输大量信息。量子力学告诉我们，半导体中的电子应该像波一样运动。对这些电子波的详细了解是设计下一代电子和光学设备所必需的。最近，使用一台建筑物大小的强大激光来快速加速半导体中的电荷，并在它们与任何其他物质相撞之前将它们粉碎在一起。原理研究小组已经能够观察到两种加速的电子波相互干扰，类似于两块扔进池塘的石头的涟漪相互作用。根据干涉的模式，原理研究小组第一次能够从实验数据中直接重建半导体中干扰电子波的数学形式。在这个项目中，研究小组利用电子波的干扰开发了一种方法，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，他们接受了半导体物理和光学方面的严格培训，最重要的是，他们解决了以前从未解决过的难题。通过这种培训，这些研究人员将处于有利地位，为工业、学术界或政府未来的信息技术发展做出贡献。这些研究人员还参与了PI广受欢迎的教育推广计划，自2005年以来，该计划为当地社区科学之夜带来了吸引人的、吸引人的和强大的“问题板”，让K-12学生获得电子电路的实践体验。技术描述：干涉测量是测量各种波中编码的信息的强大工具。固体中的带电准粒子具有波状特征，这种特征在它们的Bloch波函数中被捕捉到。2011年，原理研究小组报告了高阶边带产生的实验发现，在弱近红外激光和强THz激光的同时驱动下，半导体可以发射数十个梳状频谱中的近红外边带，梳齿被THz频率的整数倍隔开。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迈克尔逊类干涉仪的布洛赫波的干涉图，并使用一个简单的分析模型进行计算。本项目在三个方面使用了定量Bloch波干涉测量：(1)重建了块状GaAs体中电子-空穴对的有效哈密顿量、精确带隙和退相过程。这将为在技术关键的直接带隙半导体中进行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量子阱中空穴的反常位移(横向于加速电场的方向)。这将是异常速度的最干净演示之一--近70年前首次预测--并可能实现对频带局部Berry曲率的直接测量；(3)将Bloch波干涉测量扩展到Mott绝缘体，从van der Waals反铁磁体NiPS3开始，由于其极其明亮和狭窄的激子，有望成为候选对象，打开了了解强关联绝缘体电子结构的新窗口。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.