Photoelectrons are emitted from solid surfaces on which ultraviolet or
x-ray light is shone. By measuring the energy and momentum of these
photoelectrons, we can study occupied states of the solid
(photoemission spectroscopy). On the other hand, we can study
unoccupied states of the solid by detecting light emitted from
surfaces of the solid on which electrons are shone (inverse-
photoemission spectroscopy).

We are developing a high-energy-resolution inverse-photoemission
system based on dispersion matching. Using photoemission and inverse-
photoemission spectroscopy, we are studying the electronic structure
of bulk and surface of various solids. In particular, we are
interested in transition-metal compounds that show rich physical
properties such as ferromagnetism, superconductivity, and metal-
insulator transition. In transition-metal compounds, d-electrons with
spin, charge and orbital degrees of freedom are affected by
complicated lattice distortions, and display interesting electric and
magnetic properties.

We are studying the relationship between the physical properties and
electronic structure of transition-metal compounds using experimental
methods such as photoemission and inverse-photoemission spectroscopy
and theoretical methods such as model Hartree-Fock calculation. Here,
an interesting question is which kind of electronic states are
realized when d-electrons are confined at solid surface/interface.
Another interesting question is how confined d-electrons behave when
perturbed by photons. We are trying to answer these questions about
d-electrons in various transition-metal compounds.

For more information,
http://www.nanonet.go.jp/english/mailmag/2004/024b.html