Credit: Image courtesy of Ray Ashoori, Massachusetts Institute of Technology
Scientists developed a spectroscopic technique that goes beyond surface characterization and allows observation of electronic states deep within a material. This technique relies on electron tunneling, where electrons that have insufficient energy to go over an energy barrier can instead “tunnel” through it. In this technique, scientists simultaneously measured both the momentum and energy of electrons in a quantum well. The figure shows three electronic states (bands) buried beneath the sample surface. The scientists could vary parameters such as the electron density in the quantum well and the applied magnetic field, producing changes in the spectra that reveal the basic physics underlying the electronic structure.