Quantum Bicriticality in the Heavy-Fermion Metamagnet YbAgGe

TitleQuantum Bicriticality in the Heavy-Fermion Metamagnet YbAgGe
Publication TypeJournal Article
Year of Publication2013
AuthorsTokiwa Y, Garst M, Gegenwart P, Bud'ko SL, Canfield PC
Journal TitlePhysical Review Letters
Date Published09
Type of ArticleArticle
ISBN Number0031-9007
Accession NumberWOS:000324229900012
Keywordscriticality, TRANSITIONS

Bicritical points, at which two distinct symmetry-broken phases become simultaneously unstable, are typical for spin-flop metamagnetism. Interestingly, the heavy-fermion compound YbAgGe also possesses such a bicritical point (BCP) with a low temperature T-BCP approximate to 0.3 K at a magnetic field of mu H-0(BCP) approximate to 4.5 T. In its vicinity, YbAgGe exhibits anomalous behavior that we attribute to the influence of a quantum bicritical point that is close in parameter space yet can be reached by tuning T-BCP further to zero. Using high-resolution measurements of the magnetocaloric effect, we demonstrate that the magnetic Gruneisen parameter Gamma(H) indeed both changes sign and diverges as required for quantum criticality. Moreover, Gamma(H) displays a characteristic scaling behavior but only on the low-field side H <= H-BCP, indicating a pronounced asymmetry with respect to the critical field. We speculate that the small value of T-BCP is related to the geometric frustration of the Kondo lattice of YbAgGe.

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