Ultrafast Multidimensional Spectroscopy with Field Resolution and Noncollinear Geometry at Mid-Infrared Frequencies

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 (InSb) reveal a strong six-wave mixing signal and map ultrafast 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.