Beating Signals in 2D Spectroscopy: Electronic or Nuclear Coherences? Application to a Quantum Dot Model System

In 2D electronic spectroscopy, oscillatory signals have recently received increased attention. The key issue is the origin of such beating-whether it is vibrational or electronic. In analogy to the distinction between rephasing and nonrephasing contributions to 2D spectra, we separate signal components with positive and negative coherence beating frequency via a third Fourier transformation and consider two-dimensional cuts at the respective positions. We apply this approach to a model system for the description of quantum dots (QDs) and analyze the possibility to distinguish between vibrational effects associated with the longitudinal optical (LO) phonon mode and electronic fine structure splitting.