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MX-chains, more specifically, the Pd compound, and prompt further studies, for
example, on entangled dynamics in which the two collective degrees of freedom in
the electronic system and the lattice system evolve in time, affecting each other.
The second progress is the further photoconversion of the PdBr compound, that
is, the second transition from the Mott-Hubbard state to a metallic state. As we
already know that the Ni compound as another type of Mott insulator becomes
metallic after the strong photoexcitation, this sounds very likely. In fact, Matsuzaki
et al. have tried such detection and obtained a result supporting this (H. Matsuzaki,
unpublished). Although a theoretical investigation has not been tried yet, the
theorists face a novel field of dynamics in which a domain in its transient growth
process is converted again into the third phase.
The last progress we want to mention is challenges toward more detailed and
accurate understanding of this photoconversion process. So far, we have looked at
the domain growth only focusing on its coherent aspect. In this case, we mean by
the word of “coherent” a description based solely on the collective coordinate of the
domain formation. Very recently, Uemura et al. have found the generations of
various types of coherent phonons in TTF-CA during its photoconversion process
[ 51 ]. This observation suggests substantial couplings between the collective coor-
dinate and the other degrees of freedom, and tell us the necessity of a new theory
that includes such effects. In a naive image, we expect that the collective motion of
the domain growth will receive a kind of friction from the other degrees of freedom
such as phonons, magnons, electron-hole excitations, and so on. Regarding this, the
idea of quantum friction [ 52 ] is attractive, although we must keep the following two
points in mind. First, at least at the initial stage of dynamics, the relevant modes are
rather limited since the coherent phonons are observed. In this sense, this is a
different problem from that considering all the other modes as a reservoir. Second,
the domain has a translational invariance in ideal or sufficiently large systems. Not
only its spatial extension but also the motion of its center of gravity will receive
scattering effects from the other degrees of freedom. Such complexity will also be
of central interest in the very recent paper [ 53 ] and is expected to make our
understanding much deeper.
1. Nasu K (1984) J Phys Soc Jpn 53:302
2. Mishima A, Nasu K (1989) Phys Rev B 39:5758
3. Mishima A, Nasu K (1989) Phys Rev B 39:5763
4. Mishima A, Nasu K (1989) Phys Rev B 40:5593
5. Hubbard J (1963) Proc R So0063 A 276:238
6. Tanino H, Kobayashi K (1983) J Phys Soc Jpn 52:1446
7. Su WP, Schrieffer JR, Heeger AJ (1979) Phys Rev Lett 42:1698
8. Gammel JT, Saxena A, Batistic I, Bishop AR, Phillpot SR (1992) Phys Rev B 45:6408
9. Matsuzaki M, Iwano K, Aizawa T, Ono M, Kishida H, Yamashita M, Okamoto H (2004) Phys
Rev B 70:035204
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