engleski

NMR study of α-YbAlB4

α-YbAlB4 is a structural isomorph of β-YbAlB4 in which quantum criticality [1] marked by non-Fermi-liquid properties, and low- -temperature superconductivity [2], has recently been discovered at zero magnetic field. Although both compounds have similar fluctuationg valence of Yb2+/Yb3+ ions, α-YbAlB4 has a Fermi-liquid ground state with no signs of quantum critical behaviour. Such variation has been assigned to the local symmetry of the boron rings around Yb. By nuclear magnetic resonance we look for signatures of quantum criticality. Spin-lattice relaxation rate shows a clear change from the Fermi-liquid temperature dependence to a divergent non-Fermi-liquid behavior at low temperatures and finite magnetic field. Existence of a quantum critical point makes this compound ideal for studying the interplay of local symmetry and electron correlations in heavy-fermion systems. [1] Y. Matsumoto, S. Nakatsuji et al., Science 331, 316 (2011). [2] S. Nakatsuji et al., Nat. Phys. 4, 603 (2008).

criticality; heavy fermion; nmr

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