Nernst Effect in NdBa_2[Cu_{1-y}Ni_y]_3O_{7-\delta}

TL;DR

This study investigates how Ni impurities affect the Nernst effect, superconductivity, and the pseudogap in NdBa_2[Cu_{1-y}Ni_y]_3O_{7- extdelta}, revealing complex interactions that differ between optimally doped and underdoped samples.

Contribution

It provides detailed Nernst effect measurements across different doping levels, highlighting the distinct behaviors of T^ u and Tc in relation to Ni content and pseudogap temperature.

Findings

Nernst signal onset T^ u is above Tc in all samples.

In optimally doped samples, T^ u and Tc decrease with Ni doping.

In underdoped samples, T^ u remains unaffected by Ni doping up to y=0.03.

Abstract

In NdBa_2[Cu_{1-y}Ni_y]_3O_{7-\delta}, magnetic Ni-impurities suppress Tc but at the same time the pseudogap is strongly enhanced. This unique feature makes it an ideal system to study possible relations between the anomalous Nernst effect, superconductivity and the pseudogap. We present Nernst effect measurements on a series of optimally doped (O_7) and underdoped (O_{6.8}) samples with Ni contents ranging from y=0 to 0.12. In all samples an onset of the Nernst signal is found at T^\nu > Tc. For the optimally doped samples T^\nu and Tc decrease simultaneously with increasing Ni content. The underdoped samples show a different behavior, i.e. the onset of the Nernst signal is hardly affected by increasing the Ni content from y=0 to 0.03. Irrespective of the oxygen content, T^\nu clearly does not track the enhanced pseudogap temperature T*.