Delving deep into electronic properties The spectral function of a material, which reflects the distribution of its electronic states as a function of momentum and energy, carries a wealth of information on its properties. However, measuring the spectral function directly is tricky, particularly in systems inaccessible to surface probes or in insulators. Jang et al. introduce a method dubbed momentum- and energy-resolved tunneling spectroscopy, in which electrons tunnel from a probe layer to unoccupied states in a target layer deep in a heterostructure. Because the momentum and energy of the electrons are tightly controlled, the measured tunneling probability is proportional to the spectral function of the target system. Science, this issue p. 901 A method for measuring the spectral function of a material is demonstrated using gallium arsenide quantum wells. The single-particle spectral function measures the density of electronic states in a material as a function of both momentum and energy, providing central insights into strongly correlated electron phenomena. Here we demonstrate a high-resolution method for measuring the full momentum- and energy-resolved electronic spectral function of a two-dimensional (2D) electronic system embedded in a semiconductor. The technique remains operational in the presence of large externally applied magnetic fields and functions even for electronic systems with zero electrical conductivity or with zero electron density. Using the technique on a prototypical 2D system, a GaAs quantum well, we uncover signatures of many-body effects involving electron-phonon interactions, plasmons, polarons, and a phonon analog of the vacuum Rabi splitting in atomic systems.

中文翻译：

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二维电子系统的完整动量和能量分辨光谱函数

深入研究电子特性材料的光谱函数反映了其电子态的分布作为动量和能量的函数，承载了关于其特性的丰富信息。然而，直接测量光谱函数很棘手，特别是在表面探针或绝缘体无法接近的系统中。张等人。介绍一种称为动量和能量分辨隧穿光谱的方法，其中电子从探针层隧穿到异质结构深处的目标层中的未占据状态。由于电子的动量和能量受到严格控制，因此测得的隧穿概率与目标系统的光谱函数成正比。科学，这个问题 p。901 使用砷化镓量子阱展示了一种测量材料光谱函数的方法。单粒子光谱函数测量材料中电子态的密度，作为动量和能量的函数，提供对强相关电子现象的核心见解。在这里，我们展示了一种用于测量嵌入在半导体中的二维 (2D) 电子系统的完整动量和能量分辨电子光谱函数的高分辨率方法。即使对于具有零电导率或零电子密度的电子系统，该技术在存在大的外部施加磁场和功能的情况下仍然可以运行。在原型 2D 系统上使用该技术，GaAs 量子阱，