Infrared and Terahertz Nanospectroscopy of 2D Materials at the National Synchrotron Light Source II*

2D materials provide unprecedented opportunities for tailoring material properties, e.g., via exfoliation, stacking of heterostructures, and twisting.  Many fundamental material excitations of 2D materials are found at energies of a few 10 meV to a few 100 meV, i.e., in the infrared and terahertz (THz) frequency range.  Infrared nanospectroscopy provides direct access to these excitations at a spatial resolution of ~10 nm.  At the National Synchrotron Light Source II, we have established a new infrared-to-THz nanospectroscopy setup, which uniquely enables spectroscopy in the ultrabroad frequency range from 5-242 THz (175-8000 cm^‑1, 22-1000 meV, ~1-57 µm).  To demonstrate our system’s capabilities for THz nanospectroscopy, we showcase ultrabroadband synchrotron nanospectroscopy of phonons in ZnSe (~7.8 THz) and BaF₂ (~6.7 THz), as well as polariton interferometry of hyperbolic phonon polaritons in the van der Waals material GeS (6-8 THz).

The NSLS-II near-field nanospectroscopy setup at the 22IR2/MET infrared beamline is open for general user beamtime proposals. See: https://www.bnl.gov/nsls2/userguide/