Optical Measurement of the Phase-Breaking Length in Graphene
  This paper reports the experimental determination of the phase-breaking length L of conduction electrons in graphene using Raman spectroscopy. Based on the double-resonance model, we extract L from the spatial dependence of the D band susceptibility near the graphene edge. By using prior knowledge of sample properties and the excitation point-spread function we are able to determine the spatial variation of the Raman susceptibilities with high accuracy, and the results reveal a phase-breaking length L~40nm near the graphene edge. 
Luiz Gustavo Cancado, Ryan Beams, and Lukas Novotny