Dresden 2017 – wissenschaftliches Programm
TT 69.5: Hauptvortrag
Donnerstag, 23. März 2017, 17:15–17:45, HSZ 03
An Empirical Approach to the 2 mK Transition in YbRh2Si2 — •Christoph Geibel, Manuel Brando, and Alexander Steppke — Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
The Kondo lattice system YbRh2Si2 is located extremely close to a quantum critical point (QCP) separating the magnetic ordered from the paramagnetic ground state. This results in a number of very unusual properties whose origins are controversially discussed. Recently an abrupt drop in the magnetic susceptibility at 2 mK provided evidence for a combined nuclear-electronic magnetic and superconducting transition . However, the scenario proposed in , being based on a Landau model with a large number of free parameters, met some skepticism. Here we analyze the specific properties of YbRh2Si2 in view of possible mechanisms for this 2 mK transition. After introducing how hyperfine interaction works for Yb, we single out some very peculiar properties of YbRh2Si2 which result in a specific and unique situation for the interplay between 4f and nuclear moments. Below a few mK the AFM state formed at 70 mK, because of its tiny ordered 4f moment, becomes inherently unstable against the formation of a state with a larger ordered moment. Our analysis strongly supports the existence of a combined nuclear-electronic transition in the mK range in YbRh2Si2, but indicates that the ordered 4f moment should increase at this transition, in contrast to the decrease proposed in .
 E. Schuberth et al., Science 351, 485 (2016)