1202.2959 (Christian Hess)

Nernst effect of iron pnictide and cuprate superconductors: signatures
of spin density wave and stripe order    [PDF]

Christian Hess

The Nernst effect has recently proven a sensitive probe for detecting unusual
normal state properties of unconventional superconductors. In particular, it
may sensitively detect Fermi surface reconstructions which are connected to a
charge or spin density wave (SDW) ordered state, and even fluctuating forms of
such a state. Here we summarize recent results for the Nernst effect of the
iron pnictide superconductor $\rm LaO_{1-x}F_xFeAs$, whose ground state evolves
upon doping from an itinerant SDW to a superconducting state, and the cuprate
superconductor $\rm La_{1.8-x}Eu_{0.2}Sr_xCuO_4$ which exhibits static stripe
order as a ground state competing with the superconductivity. In $\rm
LaO_{1-x}F_xFeAs$, the SDW order leads to a huge Nernst response, which allows
to detect even fluctuating SDW precursors at superconducting doping levels
where long range SDW order is suppressed. This is in contrast to the impact of
stripe order on the normal state Nernst effect in $\rm
La_{1.8-x}Eu_{0.2}Sr_xCuO_4$. Here, though signatures of the stripe order are
detectable in the temperature dependence of the Nernst coefficient, its overall
temperature dependence is very similar to that of $\rm La_{2-x}Sr_xCuO_4$,
where stripe order is absent. The anomalies which are induced by the stripe
order are very subtle and the enhancement of the Nernst response due to static
stripe order in $\rm La_{1.8-x}Eu_{0.2}Sr_xCuO_4$ as compared to that of the
pseudogap phase in $\rm La_{2-x}Sr_xCuO_4$, if any, is very small.

View original: http://arxiv.org/abs/1202.2959