2007/07/01 by Oliver Dial, O. E. Dial, R. C. Ashoori +2 · 2 citations
Chemistry · Engineering · Physics and Astronomy · #Atomic physics #Chemistry #Condensed matter physics #Density of states #Electron #Electron density #Electron spectroscopy #Fermi level #Landau quantization #Molecular Junctions and Nanostructures #Particle (ecology) #Physics #Physics of Superconductivity and Magnetism #Quantum Hall effect #Quantum and electron transport phenomena #Quantum mechanics #Spectroscopy #cond-mat.mes-hall #cond-mat.str-el
paper · pdf · doi:10.1038/nature05982
published as Nature 448, 176-179 (2007) · There are formatting and minor textual differences between this version and the published version in Nature (follow the DOI link below)
openalex publication_date 2007/07/01 · arxiv created 2007/07/11 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Spectroscopic methods involving the sudden injection or ejection of electrons in materials are a powerful probe of electronic structure and interactions. These techniques, such as photoemission and tunneling, yield measurements of the "single particle" density of states (SPDOS) spectrum of a system. The SPDOS is proportional to the probability of successfully injecting or ejecting an electron in these experiments. It is equal to the number of electronic states in the system able to accept an injected electron as a function of its energy and is among the most fundamental and directly calculable quantities in theories of highly interacting systems. However, the two-dimensional electron system (2DES), host to remarkable correlated electron states such as the fractional quantum Hall effect, has proven difficult to probe spectroscopically. Here we present an improved version of time domain capacitance spectroscopy (TDCS) that now allows us to measure the SPDOS of a 2DES with unprecedented fidelity and resolution. Using TDCS, we perform measurements of a cold 2DES, providing the first direct measurements of the single-particle exchange-enhanced spin gap and single particle lifetimes in the quantum Hall system, as well as the first observations of exchange splitting of Landau levels not at the Fermi surface. The measurements reveal the difficult to reach and beautiful structure present in this highly correlated system far from the Fermi surface.