We propose that proximity of the first-order transition manifested by the quantum tricritical point (QTCP) explains non-Fermi-liquid properties of YbRh2Si2. Here, at the QTCP, a continuous phase transition changes into first order at zero temperature. The non-Fermi-liquid behaviors of YbRh2Si2 are puzzling in two aspects; diverging ferromagnetic susceptibility at the antiferromagnetic transition and unconventional power-law dependence in thermodynamic quantities. These puzzles are solved by an unconventional criticality derived from our spin fluctuation theory for the QTCP.
@article{arxiv.0710.3260,
title = {YbRh2Si2: Quantum tricritical behavior in itinerant electron systems},
author = {Takahiro Misawa and Youhei Yamaji and Masatoshi Imada},
journal= {arXiv preprint arXiv:0710.3260},
year = {2008}
}