In the beginning of this year, the MUSIQ project members from the University of Luxembourg presented a novel setup for multidimensional coherent spectroscopy with noncollinear geometry and complete field resolution in the THz range, which covers the characteristic fingerprint region of biomolecules. Thomas Deckert, MUSIQ ESR11, and PI Daniele Brida, among others, show that the setup is capable to detect signals down to a few tens of V cm-1 entirely background free and benchmark the setup with measurements on a low-bandgap semiconductor, paving the way towards the investigation of functional thin film materials, few-layer samples, and other specimen to study their coherent responses. The article has been published in New Journal of Physics and is openly accessible to all.
Energetic correlations and their dynamics govern the fundamental properties of condensed matter materials. Ultrafast multidimensional spectroscopy in the mid infrared is an advanced technique to study such coherent low-energy dynamics. The intrinsic many-body phenomena in functional solid-state materials, in particular few-layer samples, remain widely unexplored to this date, because complex and weak sample responses demand versatile and sensitive detection. Here, we present a novel setup for ultrafast multidimensional spectroscopy with noncollinear geometry and complete field resolution in the 15–40 THz range. Electric fields up to few-100 kV cm−1 drive coherent dynamics in a perturbative regime, and an advanced modulation scheme allows to detect nonlinear signals down to a few tens of V cm−1 entirely background-free with high sensitivity and full control over the geometric phase-matching conditions. Our system aims at the investigation of correlations and many-body interactions in condensed matter systems at low energy. Benchmark measurements on bulk indium antimonide reveal a strong six-wave mixing signal and map ultra-fast changes of the band structure with access to amplitude and phase information. Our results pave the way towards the investigation of functional thin film materials and few-layer samples.