In quantum materials based on transition metals, rare-earth and
actinide elements, electronic states are characterized by electrons in
orbitals d and f, combined with the solid's strong band formation. Until
now, to estimate the specific orbitals that contribute to the ground
state of these materials and determine their physical properties,
researchers have primarily relied on theoretical calculations and
In a recent study published in Nature Physics,
a team of researchers at Max Planck Institute Dresden, Heidelberg
University, University of Cologne, and DESY- Hamburg attempted to image a
material's active orbitals directly in real space, without any
modeling. The imaging technique they devised is based on s-core level
and non-resonant inelastic X-ray scattering.
"We are interested in how materials attain their properties," Hao
Tjeng, one of the researchers who carried out the study, told Phys.org.
"We want to know how these can be explained on the basis of the behavior
of the electrons in the materials. We are mostly interested in
transition metal (3d, 4d, 5d) and rare-earth-based (4f) materials,
since they offer a wealth of fascinating and tunable properties,
important for fundamental science and for numerous other applications."
When they first started working on their study, Tjeng and his
colleagues knew that the quantum mechanical equations that they would
need to solve were unsolvable, as the relevant calculations would take
an infinite amount of time. They thus realized that it would be far more
practical and useful to image the orbitals in practical experiments.
"Usually, in order to determine what type of quantum mechanical
states are realized in a material, one carries out spectroscopic
measurements," Tjeng explained. "These have their merits, but also their
limitations: one still need to do calculations to extract the
information, and quite often the results are not accurate or reliable.
We were thus looking for a new method that can provide a direct image of
the quantum mechanical state straight for the experiment. Maurits
Haverkort and I realized that inelastic x-ray scattering could provide
such an opportunity." ....