An Infrared study of the Josephson vortex state in high-Tc cuprates
  We report the results of the c-axis infrared spectroscopy of La_{2-x} Sr_x CuO_4 in high magnetic field oriented parallel to the CuO_2 planes. A significant suppression of the superfluid density with magnetic field rho_s(H) is observed for both underdoped (x=0.125) and overdoped (x=0.17) samples. We show that the existing theoretical models of the Josephson vortex state fail to consistently describe the observed effects and discuss possible reasons for the discrepancies. 
S.V.Dordevic, Seiki Komiya, Yoichi Ando, Y.J.Wang and D.N.Basov