The "washboard frequency" ω of the moving vortex lattice in untwinned YBa2Cu3O6.93 may be observed through mode-locking to an externally applied ac current of frequency ωext. The interference between ω and ωext results in jumps in the dc current-voltage characteristics when ω and ωext are harmonically related.1 The interference effect disappears in the vortex liquid state. The Hall conductivity σxy below Tc in YBCO contains contributions2 from a positive quasiparticle (qp) term (∼H) and a negative vortex term (∼1/H). The qp term is surprisingly large well below Tc and implies a large gap anisotropy and a long qp mean free path (mfp). The thermal Hall effect3 κxy is closely related to the qp σxy; κxy is produced by asymmetric scattering of qp by pinned vortices. The qp mfp at H = 0, extracted from σxy and extended to low T by κxy, increases remarkably from 90 Å at Tc to more than 0.5μm at 22 K.
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics
- Materials Science(all)
- Condensed Matter Physics