Band-dependent normal-state coherence in Sr${}_2$RuO${}_4$: Evidence from Nernst effect and thermopower measurements

Abstract

We present the first measurement on Nernst effect in the normal state of odd-parity, spin-triplet superconductor Sr${}_2$RuO${}_4$. Below 100 K, the Nernst signal was found to be negative, large, and, as a function of magnetic field, nonlinear. Its magnitude increases with the decreasing temperature until reaching a maximum around $T^{\ast }$ $\approx$ 20 - 25 K, below which it starts to decrease linearly as a function of temperature. The large value of the Nernst signal appears to be related to the multiband nature of the normal state and the nonlinearity to band-dependent magnetic fluctuation in Sr${}_2$RuO${}_4$. We argue that the sharp decrease in Nernst signal below $T^{\ast }$ is due to the suppression of quasiparticle scattering and the emergence of band-dependent coherence in the normal state. The observation of a sharp kink in the temperature dependent thermopower around $T^{\ast }$ and a sharp drop of Hall angle at low temperatures provide additional support to this picture.

4 pages, 4 figures; added figures, revised content; accepted by PRL

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• Thermopower and Entropy: lessons from Sr${}_2$RuO${}_4$
• Effect of Zn doping on magnetic order and superconductivity in LaFeAsO
• Thermoelectric properties of iron-based superconductors and parent compounds
• Giant Nernst effect in the crossover between Fermi liquid and strange metal
• Induced P-wave superfluidity within full energy-momentum dependent Eliashberg approximation in asymmetric dilute Fermi gases
• Comparative study on the thermoelectric effect of parent oxypnictides La$T$AsO ($T$ = Fe, Ni)
• Nernst response, viscosity and mobile entropy in vortex liquids
• Enhanced Seebeck coefficient through the magnetic fluctuations in Sr${}_2$Ru${}_{1-x}{M}_x$O${}_4$ ($M=$ Co, Mn)
• Negatively enhanced thermopower near a Van Hove singularity in electron-doped Sr${}_2$RuO${}_4$
• Anisotropic Seebeck coefficient of ${\mathrm{Sr}}_2\mathrm{Ru}{\mathrm{O}}_4$ in the incoherent regime
• Carrier filtering effect for enhanced thermopower in a body-centered tetragonal ruthenate
• Spin Seebeck Effect in Asymmetric Four-Terminal Systems with Rashba Spin-Orbit Coupling