A group of Kyushu University Graduate School of Engineering, Graduate School of Science, and Fukuoka Institute of Technology have succeeded in observing "Kondo resonance" in valence-ordered materials.The research results were selected as "Editor's Suggestion" in the online version of the academic journal "Physical Review B" published by the American Physical Society.
The research group focused on YbPd (ytterbium-palladium), which is one of the rare earth compounds.Rare earth compounds are characterized by exhibiting various properties by having unpaired electrons in the 4f orbit interact with conduction electrons, which are responsible for electrical conduction, in a quantum mechanical manner.It can be used in various advanced science fields, such as the constituent materials of permanent magnets used in hybrid vehicles.
It is known that YbPd realizes a unique structure in which two-dimensional planes with a valence of +2.6 and two-dimensional planes with a +2 valence are arranged alternately.Such spatially ordered arrangement of ions of the same element with different valences is called valence order, but what kind of electronic state has appeared in the valence order structure has been known so far. It was unknown.
This time, when the energy state of the electrons of YbPd was investigated in detail using point junction spectroscopy, two types of Fano resonance signals were observed.This is a quantum mechanical resonance effect caused by a single energy level interfering with a continuous energy level, and the characteristic temperature-changing fano signal was detected independently at each Yb site. It is said that it indicates that the "Kondo resonance state" has appeared.That is, it is considered that Fano resonance occurred due to interference between the Kondo resonance level and the continuous conduction electron level.
The formation of the Kondo resonance state means that the magnetic moment of the electrons in the f orbit is canceled by the conduction electrons, which is a phenomenon in which magnetic impurities magnetically combine with the conduction electrons to create a non-magnetic state. This means that the "effect" could be observed even with valence-ordered substances.This result is expected to be useful for elucidating the various magnetic properties of rare earth compounds and to lead to the development of new functional materials.
Paper information:[Physical Review B] Observation of Kondo resonance in valence-ordered YbPd
