Thermoelectric response near a quantum critical point of beta-YbAlB4 and YbRh2Si2: A comparative study

TL;DR

This study compares thermoelectric responses near quantum critical points in two Yb-based heavy fermion compounds, revealing contrasting behaviors in the Seebeck coefficient and diverging Nernst signals, shedding light on energy scale dynamics.

Contribution

It provides a comparative analysis of thermoelectric properties near QCPs in beta-YbAlB4 and YbRh2Si2, highlighting contrasting Seebeck responses and diverging Nernst coefficients.

Findings

Seebeck coefficient enhances in beta-YbAlB4 near QCP

Seebeck coefficient reduces in YbRh2Si2 near QCP

Nernst coefficient diverges in both systems near QCP

Abstract

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.