Nernst effect in high- T c superconductors

The observation of a large Nernst signal ${e}_{N}$ in an extended region above the critical temperature ${T}_{c}$ in hole-doped cuprates provides evidence that vortex excitations survive above ${T}_{c}$. The results support the scenario that superfluidity vanishes because long-range phase coherence is destroyed by thermally created vortices (in zero field) and that the pair condensate extends high into the pseudogap state in the underdoped (UD) regime. We present a series of measurements to high fields $H$ which provide strong evidence for this phase-disordering scenario. Measurements of ${e}_{N}$ in fields $H$ up to $45\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ reveal that the vortex Nernst signal has a…