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arXiv · 1206.2938

Signatures of quantum criticality in the thermopower of Ba(Fe(1-x)Co(x))2As2

S. Arsenijević·H. Hodovanets·R. Gaál·L. Forró·S. L. Bud'ko·P. C. Canfield
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Abstract

We demonstrate that the thermopower (S) can be used to probe the spin fluctuations (SFs) in proximity to the quantum critical point (QCP) in Fe-based superconductors. The sensitivity of S to the entropy of charge carriers allows us to observe an increase of S/T in Ba(Fe(1-x)Co(x))2As2 close to the spin-density-wave (SDW) QCP. This behavior is due to the coupling of low-energy conduction electrons to two-dimensional SFs, similar to heavy-fermion systems. The low-temperature enhancement of S/T in the Co substitution range 0.02 < x < 0.1 is bordered by two Lifshitz transitions, and it corresponds to the superconducting region, where a similarity between the electron and non-reconstructed hole pockets exists. The maximal S/T is observed in proximity to the commensurate-to-incommensurate SDW transition, for critical x_c ~ 0.05, close to the highest superconducting T_c. This analysis indicates that low-T thermopower is influenced by critical spin fluctuations which are important for the superconducting mechanism.

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S. Arsenijević, H. Hodovanets, R. Gaál, L. Forró, S. L. Bud'ko, P. C. Canfield. 2012-06-13. Signatures of quantum criticality in the thermopower of Ba(Fe(1-x)Co(x))2As2. https://doi.org/10.1103/physrevb.87.224508

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