Enhancement of the Nernst effect by stripe order in a high-Tc superconductor

TL;DR

This paper demonstrates that stripe order, a form of spin and charge modulation, significantly enhances the Nernst effect in high-Tc superconductors by causing Fermi surface reconstruction, challenging previous attributions to superconducting fluctuations.

Contribution

It reveals that stripe order, not just superconducting fluctuations, causes large Nernst signals in high-Tc superconductors, highlighting the Nernst effect as a probe of broken symmetry.

Findings

Stripe order induces a large positive Nernst signal.

Nernst signal changes from negative to positive across stripe order onset.

Two peaks in Nernst signal correspond to stripe order and superconductivity.

Abstract

The Nernst effect in metals is highly sensitive to two kinds of phase transition: superconductivity and density-wave order. The large positive Nernst signal observed in hole-doped high-Tc superconductors above their transition temperature Tc has so far been attributed to fluctuating superconductivity. Here we show that in some of these materials the large Nernst signal is in fact caused by stripe order, a form of spin / charge modulation which causes a reconstruction of the Fermi surface. In LSCO doped with Nd or Eu, the onset of stripe order causes the Nernst signal to go from small and negative to large and positive, as revealed either by lowering the hole concentration across the quantum critical point in Nd-LSCO, or lowering the temperature across the ordering temperature in Eu-LSCO. In the latter case, two separate peaks are resolved, respectively associated with the onset of stripe order at high temperature and superconductivity near Tc. This sensitivity to Fermi-surface reconstruction makes the Nernst effect a promising probe of broken symmetry in high-Tc superconductors.