Full Momentum and Energy Resolved Spectral Function of a 2D Electronic System

TL;DR

This paper introduces a new method to measure the full momentum and energy spectral function of 2D electronic systems, overcoming limitations of ARPES by functioning under magnetic fields and with zero conductivity or electron density.

Contribution

The authors develop a novel technique for high-resolution spectral function measurement that works in magnetic fields and for systems with zero electron density, expanding experimental capabilities.

Findings

Detected many-body effects like electron-phonon interactions and plasmons.

Observed a phonon analog of vacuum Rabi splitting.

Provided detailed dispersion and dynamics of 2D electron systems.

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.