We report measurements of in-plane electrical and thermal transport properties in the limit T→0 near the unconventional quantum critical point in the heavy-fermion metal β-YbAlB4. The high Kondo temperature TK≃ 200 K in this material allows us to probe transport extremely close to the critical point, at unusually small values of T/TK<5×10−4. Here we find that the Wiedemann-Franz law is obeyed at the lowest temperatures, implying that the Landau quasiparticles remain intact in the critical region. At finite temperatures we observe a non-Fermi liquid T-linear dependence of inelastic scattering processes to energies lower than those previously accessed. These processes have a weaker temperature dependence than in comparable heavy fermion quantum critical systems, and suggest a new temperature scale of T∼0.3K which signals a sudden change in character of the inelastic scattering.
@article{arxiv.1408.0033,
title = {Intact Quasiparticles at an Unconventional Quantum Critical Point},
author = {M. L. Sutherland and E. C. T. O'Farrell and W. H. Toews and J. Dunn and K. Kuga and S. Nakatsuji and Y. Machida and K. Izawa and R. W. Hill},
journal= {arXiv preprint arXiv:1408.0033},
year = {2015}
}