engleski

Anisotropy-driven quantum criticality in an intermediate valence system

Intermetallic compounds containing f-electron elements have been prototypical materials for investigating strong electron correlations and quantum criticality (QC). However, intermediate valence (IV) compounds have been mainly outside the focus of research on QC since the presence of large characteristic energy scales requires application of high magnetic fields or pressures to notably modify their properties or induce new phases. In contrast, QC has been discovered at zero magnetic field [1, 2] in b-YbAlB4, and at low magnetic field in pure [3] and Fe-doped [4] a-YbAlB4 systems. Both polymorphs have IV of +2.75 and +2.73, respectively, with a fluctuating valence scale of T0 ~ 200 K. We present the results of a complete set of thermodynamic, magnetotransport and microscopic experimental techniques used to probe the QC in the pure a-YbAlB4 and establish a complete picture of the system. The presence of quantum critical properties even in the pure system indicates that YbAlB4 family is close to several electronic instabilities. The presence of a diverse quantum critical behaviour in the YbAlB4 family means that a robust physical mechanism emerges in the presence of strong electron anisotropy - unaffected by the change of local symmetry. By combining the results of complementary techniques we find that the hybridization anisotropy is the key ingredient for achieving QC here. This offers a new route for overcoming the large valence energy scale. [1] S. Nakatsuji et al., Nature Physics 4, 603 (2008). [2] Y. Matsumoto et al., Science 331, 316 (2011). [3] M. S. Grbić et al., in preparation

necjelobrojna valencija ; anizotropija ; kvantna kritičnost

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