Investigating Ultracold Polarons with Ramsey Spectroscopy: From 1D to Multidimensional

Ramsey spectroscopy is a technique similar to the well-known nuclear magnetic resonance (NMR) interferometry, which manipulates internal degrees of freedom (e.g., pseudospin instead of spin) and observes the interference determined by the surrounding many-body environment. The conventional Ramsey spectroscopy typically shows the signal as a function of a single variable, and thus, it is called one-dimensional (1D). In this talk, I will first describe studying the 1D Ramsey spectroscopy of a heavy impurity embedded in a paired two-component Fermi gas at the crossover from a Bose-Einstein condensate (BEC) to a Bardeen-Cooper-Schrieffer (BCS) superfluid, which provides an essential exact polaron model [1, 2]. Secondly, I will discuss how to push the well-established 1D Ramsey spectroscopy into multidimensional (MD) in the same spirit of MD NMR [3]. This new tool enables the observation of nonlinear nonequilibrium dynamics of an impurity in ultracold Fermi gases manipulated by a series of radiofrequency (RF) pulses at different times and reveals many-body correlations unfolded in conventional 1D spectroscopy.



[1] Jia Wang, Xia-Ji Liu, and Hui Hu, PRL 128, 175301 (2022)

[2] Jia Wang, Xia-Ji Liu, and Hui Hu, PRA 105, 043320 (2022)

[3] Jia Wang, PRA 107, 013305 (2023)