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arXiv · 1905.11660

Strain-derivative of thermoelectric properties: a sensitive probe for nematicity

Federico Caglieris·Christoph Wuttke·Xiaochen Hong·Steffen Sykora·Rhea Kappenberger·Saicharan Aswartham·Sabine Wurmehl·Bernd Büchner·Christian Hess
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Abstract

The nematic instability of iron-based superconductors is an undebatable ingredient of the physics of iron-based superconductors. Yet, its origin remains enigmatic as it involves a fermiology with an intricate interplay of lattice-, orbital- and spin- degrees of freedom. It is well known that thermoelectric transport is an excellent probe for revealing even subtle signatures of instabilities and pertinent fluctuations. In this paper, we report a strong response of the thermoelectric transport properties of two underdoped 1111 iron-based superconductors to a vanishingly small strain. By introducing the strain-derivative of the Seebeck and the Nernst coefficients, we provide a novel description of the nematic order parameter, proving the existence of an anisotropic Peltier-tensor beside an anisotropic conductivity-tensor. Our measurements reveal that the transport nematic phenomenology is the result of the combined effect of both an anisotropic scattering time and Fermi surface distortions, pointing out that in a realistic description, abreast of the spin-fluctuations also the orbital character is a fundamental ingredient. In addition, we show that nematic fluctuations universally relax in a Curie-Weiss fashion above T_S in all the elasto-transport measurements and we provide evidences that nematicity must be band-selective.

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Federico Caglieris, Christoph Wuttke, Xiaochen Hong, Steffen Sykora, Rhea Kappenberger, Saicharan Aswartham, Sabine Wurmehl, Bernd Büchner, Christian Hess. 2019-05-28. Strain-derivative of thermoelectric properties: a sensitive probe for nematicity. https://doi.org/10.1038/s41535-021-00324-7

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