|approved||summary.pdf||2015-03-28 12:24:30||Mads Trolle|
Author: Mads L. Trolle
Requested Type: Oral
Submitted: 2015-03-12 04:27:59
Co-authors: T.G. Pedersen, K. Pedersen
Aalborg East, 9220
Efforts toward extracting information from 2D transition metal dichalcogenide (TMD) samples, using second-harmonic (SH) generation as a spectroscopic tool, are presently hampered by: (i) The lack of benchmark SH spectra from pristine samples recorded in a frequency range allowing resolution of multiple excitonic features and (ii) by the lack of theoretical understanding of the underlying electronic mechanisms – in particular, the interplay between SH optical processes and excitonic many-body effects. In this talk, we present experimental SH spectra generated in both thick flakes and bulk crystals of MoS2. These spectra are recorded in a broad pump photon energy range between 0.85 and 1.7 eV, allowing simultaneous resolution of the fundamental A/B excitons and the powerful C resonance. We interpret the measured response in terms of stacked and electronically decoupled 2D layers, each with a sheet SH response tensor which alternates in phase according to layer. Using this model, we are able to derive the modulus of the effective response tensor. Moreover, we compare directly with our recent quantum simulation of the SH response generated in three-layer MoS2, taking also excitonic effects into account. These results allow for interpretation of experimental results, e.g. assignment of recorded spectral features to specific excitonic resonances.
This work contains both 2.0 "Theory of surface optical responses" and 4.0 "Nonlinear optics at surfaces: Experiment"