T dependence of nuclear spin-echo decay at low temperatures in YbRh2Si2

Abstract

The authors report $^{29}\mathrm{Si}$ nuclear spin-echo oscillations and decay measurements on a single crystal of ${\mathrm{YbRh}}_{2}{\mathrm{Si}}_{2}$. These quantities are found to be $T$ independent from 300 K down to $\ensuremath{\sim}20$ K, showing, however, a strong $T$ dependence below 20 K. These results indicate that electronic states near the Fermi level are modified at low temperatures. The observed spin-echo oscillations can be interpreted with the Ruderman-Kittel and pseudodipolar interactions between nearest-neighbor Si nuclei driven by conduction electron scattering at the Fermi surface. Possible modifications to the Fermi surface at low temperatures are discussed.