Fermi liquid theory, the standard theory of metals, has been challenged by a number of observations of anomalous metallic behavior found in the vicinity of a quantum phase transition. The breakdown of the Fermi liquid is accomplished by fine-tuning the material to a quantum critical point using a control parameter such as the magnetic field, pressure, or chemical composition. Our high precision magnetization measurements of the ultrapure f-electron based superconductor {\beta}-YbAlB4 demonstrate a scaling of its free energy indicative of zero-field quantum criticality without tuning in a metal. The breakdown of Fermi-liquid behavior takes place in a mixed-valence state, in sharp contrast with other known examples of quantum critical f-electron systems that are magnetic Kondo lattice systems with integral valence.
@article{arxiv.1101.4302,
title = {Quantum Criticality without Tuning in the Mixed Valence Compound beta-YbAlB4},
author = {Yosuke Matsumoto and Satoru Nakatsuji and Kentaro Kuga and Yoshitomo Karaki and Naoki Horie and Yasuyuki Shimura and Toshiro Sakakibara and Andriy H. Nevidomskyy and Piers Coleman},
journal= {arXiv preprint arXiv:1101.4302},
year = {2015}
}
Comments
26 pages, 7 figures including supporting online matelials