Enhanced Electron-Phonon Coupling at Metal Surfaces

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***NON_TECHNICAL***Treating the dynamic interaction of the electrons and the atoms or molecules in a solid is difficult but essential if functionality is to be designed into advanced materials. In textbooks this interaction is handled by using the Born-Oppenheimer Approximation (BOA), which allows scientists to consider the slow-moving atoms to be frozen in space in their average positions while the more energetic electrons do their thing. But a multitude of important chemical, physical, and biological phenomena are driven by violations of the BOA. Breakdown in the BOA results from low-energy excitations of the electrons near what is known as the Fermi energy coupling with vibrational excitations of the solid. The resulting vibronic interactions are a necessary ingredient in any process that makes or breaks a covalent bond or in conventional superconductivity, which is driven by the electron-lattice interaction. Many of the emergent properties of complex materials or artificially nanostructured materials result from coupling of the electronic and lattice (atom) motion in systems that are inherently anisotropic. This project will use a newly developed data analysis procedure to extract the details of this coupling between the electrons and the lattice from high-resolution spectrocopic data. Undergraduates, graduates and post docs will be involved with state-of-the-art instrumentation and materials preparation. This award is co-funded by NSF's Division of Materials Research and the Department of Energy's Office of Basic Energy Sciences.***TECHNICAL***This individual investigator award supports an experimental investigation of the electron-phonon coupling (EPC) at metal surfaces. A newly developed data analysis procedure enables the spectroscopic features of this coupling to be exacted from high-resolution angle-resolved photoemssion spectroscopy (ARPES) data. For the first time in very anisotropic systems it is possible to "see" which vibrational modes couple to which electrons. This procedure will be applied to a variety of materials, ranging from layered transition-metal oxides, MBE grown thin films of MgB2, and clean and modified surfaces. ARPES measurements will be correlated with scanning tunneling spectroscopy measurements of the EPC and inelastic electron scattering measurements of the phonon dispersion at the surface. A world wide collaboration has been created to take full advantage of theoretical and experimental advances in this field. This research project offers an ideal training ground for undergraduates, graduate students, post docs and visiting scientists, exposing them the state-of-the-art instrumentation, sophisticated growth procedures and close coupling with theory. This award is co-funded by NSF's Division of Materials Research and the Department of Energy's Office of Basic Energy Sciences.