Nernst effect and diamagnetic response in superconducting cuprates (Vol. 41, No. 6)

One of the central puzzles of the high-temperature cuprate superconductors is the nature of the pseudo-gap regime that extends from the parent Mott insulator to at least optimal doping and up to several hundred degrees Kelvin. Though it is unlikely that the entire pseudo-gap region is directly related to superconductivity, there is compelling experimental evidence of anomalously strong superconducting fluctuations within the pseudo-gap.

Two phenomena have particularly high sensitivities to the presence of superconductivity, even local or fluctuating one: the diamagnetism and the Nernst effect. The diamagnetic part of field-induced magnetization can reveal the presence of even isolated superconductivity inclusions, as they expel magnetic field. The Nernst effect is a thermal analogue of the conventional Hall effect – the transverse voltage generation in response to the heat current flow in a magnetic field. The Nernst effect in metals is typically very weak; however, in the presence of superconductivity it is greatly enhanced due to the thermal drift of vortices, which induces voltage via the Josephson relationship.

We examine the possibility that the experimentally observed enhancement of superconducting fluctuations above the superconducting transition temperature in the underdoped cuprates is caused by stripes -- an intrinsic electronic inhomogeneity, common to hole-doped cuprates. By evaluating the strengths of the diamagnetic response and the Nernst effect within a striped SC model, we find results that are qualitatively consistent with the experimental observations. We make a prediction for anisotropic thermopower in detwinned samples that can be used to further test the proposed scenario.