CHINESE JOURNAL OF PHYSICS VOL. 36, NO. 2-11 APRIL 1998 Vortex Lattice Structure and Josephson Plasma in High T, Superconductors M. TachikizyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA 1 2, S. E. Shafranjuk213, and X. Hu’ N ational Research Institute for Metals, 1-2-1 Sengen, Tsukuba 305, Japan 2CREST, Japan Sczen ce and Technology Corporation (JST) R esearch Instztute of Electrzcal Communication, 2-l-l Katahira, Aobaku, Sendai 980, Japan [Received December 20. 1997) The nature of the Josephson vortices induced by an external magnetic field applied parallel to the CuO2 layers in a high T, superconductor end it ofthe Josephson plasma in the presence ofthe vortices are theoretically investigated. The ordered structure ofthe vortices is obtained by solving the nonlinear differential equation for the interlayer phase difference in a stacked system of Josephson junctions. The current distribution in the Josephson vortex is highly anisotropic and the vortices are arranged in straight chains, dissimilar to hexagonal lattices of Abrikosov and pancake vortices. The appearance of the chain structure in the system is also confirmedby a Monte Carlo simulation. The Josephson plasma is a coupled oscillation of the phase difference between the layers and of the electromagnetic field. The vortices modify the phase difference and thus strongly influence the Josephson plasma oscillation. Therefore, the dispersion spectra of the longitudinal and transverse plasma waves in the presence of the vortices are strongly -dependent on the strength of an external magnetic field and temperature. PACS. 74.72.-h ~ High-Tc cuprates. PACS. 74.50.+r Proximity effects, weak links. tunneling phenomena, and Josephson effects. PACS. 74.60.Ge - Flux pinning, flux creep, and flux-line lattice dynamics. I. Introduction The cuprate high T, superconductors have a microscopic layered structure in which the superconducting CuO2 layers are coupled by the intrinsic Josephson effect through the block layers as seen from Fig. 1. In the crystals a unique excitation called Josephson plasma arises. The plasma wave is a composite of the wave of the Josephson current flowing along the c axis and the electromagnetic wave. The plasma waves propagating along the c axis and in the a-b plane are respectively the longitudinal and transverse plasma waves, and each has different nature. We begin with a brief review of the nature of the plasma waves zyxwvutsrqponml M The Josephson current flowing between the 1 th and (I+ l)th layer of the CuO2 layers is expressed by 171 @ 1998 THE PHYSICAL SOCIETY OF THE REPUBLIC OF CHINA