Two Phase Collective Modes in Josephson Vortex Lattice in Intrinsic Josephson Junction Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$

I. Kakeya, T. Wada, R. Nakamura +1

Josephson plasma excitations in the high $T_c$ superconductor Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$ have been investigated in a wide microwave frequency region (9.8 -- 75 GHz), in particul…