Special CPM Seminar

A Pillar of Condensed Matter Spectroscopy Fails Inspection

Eric Heller

Harvard University

The established approaches or “pillars” of condensed matter spectroscopy include models and approximations allowing one to ascend to more topical questions. But the models involve complex many body systems and understandably fall well short of precision. The models should remain under question and be subject to revision. One such pillar is the universal approximation taking electronic transition moments to be independent of nuclear (and phonon coordinates). Releasing electronic transition moments from this traditional bondage allows resonant indirect transitions and associated phonon production without requiring virtual electron-phonon scattering. Virtual electron-phonon scattering misses key indirect transitions necessary to understand the spectroscopy of graphene and more importantly, its electronic relaxation and dynamics. Many experimental facts become clear in this new guise, including recent ultrafast pump-probe measurements.