The thermoelectric coefficients have been measured on the Yb-based heavy fermion compounds beta-YbAlB4 and YbRh2Si2 down to a very low temperature. We observe a striking difference in the behavior of the Seebeck coefficient, S in the vicinity of the Quantum Critical Point (QCP) in the two systems. As the critical field is approached, S/T enhances in beta-YbAlB4 but is drastically reduced in YbRh2Si2. While in the former system, the ratio of thermopower-to-specific heat remains constant, it drastically drops near the QCP in YbRh2Si2. In both systems, on the other hand, the Nernst coefficient shows a diverging behavior near the QCP. The results provide a new window to the way various energy scales of the system behave and eventually vanish near a QCP.
@article{arxiv.1202.2753,
title = {Thermoelectric response near a quantum critical point of beta-YbAlB4 and YbRh2Si2: A comparative study},
author = {Y. Machida and K. Tomokuni and C. Ogura and K. Izawa and K. Kuga and S. Nakatsuji and G. Lapertot and G. Knebel and J. -P. Brison and J. Flouquet},
journal= {arXiv preprint arXiv:1202.2753},
year = {2015}
}