Multidimensional spectroscopy of heavy impurities in ultracold fermions

We investigate the system of a heavy impurity immersed in degenerated Fermi gas, where impurity's internal degree freedom (pseudospin) is manipulated by series radiofrequency (RF) pulses at several different times. Applying functional determinant approach, we carry out an essentially exact calculation Ramsey-interference-type responses to RF pulses. These are universal functions multiple time intervals between for all and can be regarded as multidimensional (MD) spectroscopy domain. A Fourier transformation gives MD frequency domain, providing insightful information on many-body correlation relaxation via cross-peaks, e.g., off-diagonal peaks two-dimensional spectrum. features inaccessible conventional, one-dimensional absorption Our scheme provides new method nonequilibrium physics beyond linear response regime with accessible tools cold atoms.