[Publication] A unique interplay of Kondo behavior and charge density wave in the YbPd compound

The valence state of Yb was investigated by Hard X-ray photoemission spectroscopy as a function of temperature through the charge density wave transition. At high temperature the structure is cubic with one Yb site and below the charge density wave transition temperature (130 K), the charge modulation leads to a tetragonal phase with two Yb sites.

By using simulations based on a single impurity Anderson model, they were able to deduce the Yb electronic configuration of the two sites. One Yb sublattice is nearly trivalent and  orders magnetically at low temperature whereas the other one is in an intermediate valence state with a non-magnetic character and a very large Kondo temperature.

They have conjectured that the Kondo effect could be the driving mechanism of the charge density wave transition. The Kondo energy scale exhibits the Bardeen-Cooper-Schrieffer (BCS) temperature dependence which characterizes the order parameter of charge density waves.

Title: Dual Kondo effect charge ordering and zero thermal expansion in a correlated intermetallic

Authors: Liao, YF., Tegomo Chiogo, B., Clausse, T.,  Mazet, T., Tsuei KD.,  Malterre, D., Chainani, A.

Journal: Communications Materials

Date of publication (online): April 2022

Link: https://doi.org/10.1038/s43246-022-00243-5

Image caption:
Left: Core level photoemission at several temperatures.
Right: Temperature dependence of the Yb valence of the two sites in the tetragonal et cubic phases. Order parameter of the charge density wave phase exhibiting a BCS dependence