Speaker: Dr. Bongjune Kim, National Tsing Hua University 

Time:  1:20 p.m, 4/12 

Place:  R124, NTHU Physics Department

Title: 
Experimental study on the system of weakly-interacting many-body of Rydberg 
polaritons 

Abstract:
     Due to the strong dipole-dipole interaction (DDI) and a dipole blockade effect 
of Rydberg atoms, the combination of Rydberg atoms and electromagnetically induced 
transparency (EIT) has been widely studied in the strong interaction regime. In this 
talk, we will discuss on the utilizing of weakly-interacting many-body system of 
Rydberg polaritons. In our experiment, the Rydberg polaritons are generated based on 
the ladder-type EIT system with laser-cooled 87Rb atoms. To realize a weakly-
interacting many-body system formed by Rydberg polaritons, a low principle number of 
Rydberg state |32D5/2> is employed. The DDI-induced absorption coefficient and phase 
shift of the system are experimentally observed by increasing the probe Rabi 
frequency or, equivalently, the density of Rydberg-state atoms. The absorption 
coefficient is determined by the measurement of probe field transmission. The phase 
shift is measured with the beat note interferometer. The measured results are in 
good agreements with our theoretical model based on the mean-field theory. Finally, 
we experimentally observed smaller transverse momentum distribution of probe beam 
from the output probe beam profiles taken by EMCCD after the interaction. This 
observation demonstrates thermalization process in weakly-interacting many-body 
system of Rydberg polaritons.