Signatures of quantum criticality in the thermopower of Ba(Fe1-xCox)(2)As-2

TitleSignatures of quantum criticality in the thermopower of Ba(Fe1-xCox)(2)As-2
Publication TypeJournal Article
Year of Publication2013
AuthorsArsenijevic S, Hodovanets H, Gaal R, Forro L, Bud'ko SL, Canfield PC
Journal TitlePhysical Review B
Date Published06
Type of ArticleArticle
ISBN Number1098-0121
Accession NumberWOS:000320609300003
Keywordsbafe2(as1-xpx)(2), critical-point, cuprate, fermi-liquid behavior, instability, iron arsenide superconductor, resistivity, superconductors, surface, temperature, transition

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(Fe1-x Co-x)(2)As-2 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 nonreconstructed hole pockets exists. The maximal S/T is observed in proximity to the commensurate-to-incommensurate SDW transition, for critical x(c) approximate to 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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