Anisotropy-driven quantum criticality in an intermediate valence system.

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O'Farrell, Eoin CT 
Matsumoto, Yosuke 
Brando, Manuel 

Intermetallic compounds containing f-electron elements have been prototypical materials for investigating strong electron correlations and quantum criticality (QC). Their heavy fermion ground state evoked by the magnetic f-electrons is susceptible to the onset of quantum phases, such as magnetism or superconductivity, due to the enhanced effective mass (m*) and a corresponding decrease of the Fermi temperature. However, the presence of f-electron valence fluctuations to a non-magnetic state is regarded an anathema to QC, as it usually generates a paramagnetic Fermi-liquid state with quasiparticles of moderate m*. Such systems are typically isotropic, with a characteristic energy scale T0 of the order of hundreds of kelvins that require large magnetic fields or pressures to promote a valence or magnetic instability. Here we show the discovery of a quantum critical behaviour and a Lifshitz transition under low magnetic field in an intermediate valence compound α-YbAlB4. The QC origin is attributed to the anisotropic hybridization between the conduction and localized f-electrons. These findings suggest a new route to bypass the large valence energy scale in developing the QC.


Funder: U.S. National Science Foundation CAREER grant no. DMR-1350237

Funder: RCUK | Engineering and Physical Sciences Research Council (EPSRC); doi:

Funder: Royal Society; doi:

Funder: CIFAR as a Fellow of the CIFAR Quantum Materials Research Program

Article, /639/766/119/2795, /639/766/119/995, /639/766/119/997, article
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Nat Commun
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Springer Science and Business Media LLC
Deutsche Forschungsgemeinschaft (German Research Foundation) (BR 4110/1-1)
Welch Foundation (C-1818)
DOE | SC | Basic Energy Sciences (BES) (DE-SC0019331)