Anisotropic heavy-Fermi-liquid formation in valence-fluctuating alpha-YbAlB4

Article

关键词: SUPERCONDUCTIVITY;    METAMAGNETISM;    RESISTIVITY;    TRANSITION;    YB;   

DOI  :  10.1103/PhysRevB.84.125126

来源: SCIE

【 摘 要 】

alpha-YbAlB4 is the locally isostructural polymorph of beta-YbAlB4, the first example of a Yb-based heavy fermion superconductor that exhibits pronounced non-Fermi-liquid behavior above T-c. Interestingly, both alpha-YbAlB4 and beta-YbAlB4 have strongly intermediate valence. Our single-crystal study of the specific heat, magnetization, and resistivity has confirmed the Fermi-liquid ground state of alpha-YbAlB4 in contrast to the quantum criticality observed in beta-YbAlB4. Both systems exhibit Kondo lattice behavior with the characteristic temperature scale T*similar to 8 K in addition to a valence-fluctuation scale similar to 200 K. Below T*, alpha-YbAlB4 forms a heavy-Fermi-liquid state with an electronic specific heat coefficient gamma similar to 130 mJ/mol K-2 and a large Wilson ratio greater than 7, which indicates ferromagnetic correlation between Yb moments. A large anisotropy in the resistivity, which is one of the largest in heavy fermions, suggests that the hybridization between 4f and conduction electrons is much stronger in the ab plane than along the c axis, indicating this is an excellent system to study for revealing the anisotropic hybridization effects. The strongly anisotropic hybridization as well as the large Wilson ratio is the key to understanding the unusual Kondo lattice behavior and heavy-fermion formation in mixed-valence compounds.

【 授权许可】

Free