Electronuclear Transition into a Spatially Modulated Magnetic State in ${\mathrm{YbRh}}_{2}{\mathrm{Si}}_{2}$

Electronuclear Transition into a Spatially Modulated Magnetic State in ${YbRh}_{2} {Si}_{2}$

J. Knapp, L. V. Levitin, J. Nyéki, A. F. Ho, B. Cowan, J. Saunders, M. Brando, C. Geibel, K. Kliemt, and C. Krellner

Phys. Rev. Lett. 130, 126802 – Published 23 March 2023

Abstract

The nature of the antiferromagnetic order in the heavy fermion metal ${YbRh}_{2} {Si}_{2}$ , its quantum criticality, and superconductivity, which appears at low mK temperatures, remain open questions. We report measurements of the heat capacity over the wide temperature range $180 μ K - 80 mK$ , using current sensing noise thermometry. In zero magnetic field we observe a remarkably sharp heat capacity anomaly at 1.5 mK, which we identify as an electronuclear transition into a state with spatially modulated electronic magnetic order of maximum amplitude $0.1 μ_{B}$ . We also report results of measurements in magnetic fields in the range 0 to 70 mT, applied perpendicular to the $c$ axis, which show eventual suppression of this order. These results demonstrate a coexistence of a large moment antiferromagnet with putative superconductivity.