UC Santa Cruz

The 3D topological insulator material Bi2Se3 is characterized with angle-resolved photoemission spectroscopy (ARPES) energy-momentum intensity spectra at various temperatures. High quality samples with relatively small band gaps and a low energy Dirac point were used. An ideal resolution was deter- mined to be taken at photon energy of 11eV. Scattering interaction at the surface can come from three main sources: electron-phonon, surface impurity, or electron-electron scattering, between the surface and the bulk conduction bands. Momemtum- and Energy- Distribution Curves (MDC and EDC) fits were modeled with Gaussian convoluted Lorentzian and extremely-correlated Fermi liquid theory, respectively. By comparing the binding energy at different temperatures for regions near the Fermi edge and near the Dirac point, and observing an increase in MDC self-energy near the Fermi edge, we conclude that a source of interaction is through phonon coupling channels. By calculating the coupling constant λ from self-energy at various temperatures, we present a very low value of λ = 0.049 ± 0.007 which supports our conclusion that phonon coupling must be incorporated into the theory to provide accurate fit models. Data was taken at beam line 5-4 at the Stanford Synchrotron Radiation Lightsource in Menlo Park, with samples prepared by Genda Gu’s group at Brookhaven National Laboratory.