Statics and dynamics of flux line lattices of high-Tc superconductors

Abstract

The authors investigate the energy, elastic modulus and normal modes of oscillation of flux line lattices. To deal with the long range nature of the flux line potential, the Ewald sum technique was used. The dependence of the normal modes as a function of the transverse wavevector in the 2D hexagonal Brillouin zone and the z wavevector kz is discussed in detail. They found two normal modes corresponding to the shear and the compression of the lattice. The frequencies of these two are usually very different from each other. Because of the long range nature of the potential, the compressive mode behaves like a plasma oscillation. At zero momentum the excitations are gapless, because the potentially is exponential in character at large distances. At a finite z wavevector they found that the transverse frequencies drop off rapidly as the transverse wavevector is increased. The elastic moduli are compared with those computed using a continuum approximation by Sudbo and co-workers. Quantitative differences are found in the low field, small k region as well as the high field, large k region.