Probing electrodynamical properties of the edge states in a quantum Hall   system by surface photovoltage spectroscopy
  An importent question regarding the dissipation-less current carried by the edge states in a quantum Hall system is understanding the results of the electrodynamical interaction among the mobile electrons in the quantum mechanical limit under a magnetic field B. The interaction affects the transport parameters, the transverse electric field and the electron velocity. We have developed a new surface photovoltage spectroscopic technique to measure the parameters from the transition energies between the electron and heavy hole edge states. We observe that the measured electron velocity and transverse (Hall) electric field increase as B^{1/2} and B^{3/2} respectively. 
B. Karmakar, G. H. Dohler and B. M. Arora