Quantum criticality without tuning in the mixed valence compound beta-YbAlB4.
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 by 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 β-YbAlB(4) demonstrate a scaling of its free energy that is indicative of zero-field quantum criticality without tuning in a metal. The breakdown of Fermi liquid behavior takes place in a mixed-valence state, which is in sharp contrast with other known examples of quantum critical f-electron systems that are magnetic Kondo lattice systems with integral valence.
Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan.
Yosuke
Y
Matsumoto
Satoru
S
Nakatsuji
Kentaro
K
Kuga
Yoshitomo
Y
Karaki
Naoki
N
Horie
Yasuyuki
Y
Shimura
Toshiro
T
Sakakibara
Andriy H
AH
Nevidomskyy
Piers
P
Coleman