Title: Full Momentum and Energy Resolved Spectral Function of a 2D Electronic System,
Abstract: The single-particle spectral function measures the density of electronic
states (DOS) in a material as a function of both momentum and energy, providing
central insights into phenomena such as superconductivity and Mott insulators.
While scanning tunneling microscopy (STM) and other tunneling methods have
provided partial spectral information, until now only angle-resolved
photoemission spectroscopy (ARPES) has permitted a comprehensive determination
of the spectral function of materials in both momentum and energy. However,
ARPES operates only on electronic systems at the material surface and cannot
work in the presence of applied magnetic fields. Here, we demonstrate a new
method for determining the full momentum and energy resolved electronic
spectral function of a two-dimensional (2D) electronic system embedded in a
semiconductor. In contrast with ARPES, the technique remains operational in the
presence of large externally applied magnetic fields and functions for
electronic systems with zero electrical conductivity or with zero electron
density. It provides a direct high-resolution and high-fidelity probe of the
dispersion and dynamics of the interacting 2D electron system. By ensuring the
system of interest remains under equilibrium conditions, we uncover delicate
signatures of many-body effects involving electron-phonon interactions,
plasmons, polarons, and a novel phonon analog of the vacuum Rabi splitting in
atomic systems.