Observation of superluminal propagation at negative group velocity in C60 solution

Abstract

The authors observed the superluminal propagation at negative group velocity in C60 toluene solution firstly. The theoretical analysis was made based on density matrix model of superluminal propagation. The simulation result was well consistent with experimental measurement. The largest time advancement of 3.58ms was got at 5.6×10−4mol∕l of sample concentration; the corresponding group velocity is −0.28m∕s.