Chemistry Reference
In-Depth Information
Chapter 5
Photoinduced Phase Transitions in MX-Chain
Compounds
Hiroyuki Matsuzaki and Hiroshi Okamoto
5.1
Introduction
The control of phase transitions and related macroscopic properties in solids by
photoexcitation, which is called “photoinduced phase transition (PIPT)” [
1
,
2
], is
now attracting considerable attention as a novel mechanism for photoswitching of
optical, transport, and magnetic properties. Several characteristic PIPTs such as
neutral (
N
) and ionic (
I
) transitions [
3
-
10
], insulator to metal transitions [
11
-
25
],
and diamagnetic to paramagnetic or ferromagnetic transitions [
26
-
39
] have been
indeed demonstrated thus far. In some of these PIPTs, the photoinduced phases are
fairly unstable and their lifetimes are very short, being of picosecond (ps) or sub-ps
order. Such ultrafast responses of PIPTs make us expect the generation of a new
field involving both basic science and device applications.
From a scientific point of view, the ultrafast nonequilibrium dynamics of PIPTs
in solids will be an important subject. By a photoexcitation, charge ordering (CO)
and lattice distortions stabilizing CO as well as spin orderings can be dynamically
melted or reconstructed as a result of competitive interplays among charge, spin,
and lattice degrees of freedom in both photoexcited states and ground states.
Generally speaking, PIPTs show a wide variety of dynamics depending on
materials and the time scales of their dynamics change over a wide range from
seconds to femtoseconds (fs). Such a variety of PIPT dynamics originates from the
Search WWH ::
Custom Search